Abstract
Envelope (E) protein is one of the structural viroporins (76–109 amino acids long) present in the coronavirus. Sixteen sequentially different E-proteins were observed from a total of 4917 available complete SARS-CoV-2 genomes as on 18th June 2020 in the NCBI database. The missense mutations over the envelope protein across various coronaviruses of the β-genus were analyzed to know the immediate parental origin of the envelope protein of SARS-CoV-2. The evolutionary origin is also endorsed by the phylogenetic analysis of the envelope proteins comparing sequence homology as well as amino acid conservations.
Keywords: Envelope protein, SARS-CoV-2, COVID-19, Viroporin, Amino acid conservation, Phylogeny
1. Introduction
A novel coronavirus has been causing the ongoing pandemic which is certainly life threatening as our world is experiencing since December 2019 [1]. Coronaviruses (CoV), containing positive-sense RNA as genetic material, cause primarily respiratory infections in humans and a broad range of animals. Recently several new human coronaviruses, including severe acute respiratory syndrome coronavirus (SARS-CoV), MERS-CoV and SARS-CoV-2, were identified, which attract scientists in comprehensive understanding of viruses and identification of antiviral targets for development of therapeutic treatments. A CoV contains several proteins (structural, non-structural, accessory, etc.) among which two major structural proteins of the coronaviruses (CoVs) are spike (S) and membrane (M) glycoproteins [2]. Every Coronavirus of the β − genus does contain an envelope (E) protein, containing 75 to 84 amino acids, which plays essential roles in virus assembly, budding, morphogenesis, entry in the host cell and regulation of other cellular functions [3]. This E protein is an integral membrane protein mainly found in the ERGIC (Endoplasmic Reticulum-Golgi Intermediate Compartment) of cells transfected with a plasmid encoding E protein or infected with SARS-CoV [4]. Envelope protein of SARS-CoV-2 is 75 amino acids long, and it possesses three important domains viz. (N)-terminus containing 7–9 hydrophilic region, transmembrane domain (TMD) containing 29 amino acid residues with a high leucine/isoleucine/valine content (hydrophobic region) and (C)-terminus with hydrophilic region (Fig. 1 ) [5].
Fig. 1.
Domains of the envelope protein of β-CoVs.
The envelope (E) protein of the coronavirus (CoV) of the β-genus famiy forms ion channels [6]. The transmembrane domain (TMD) of the E protein is responsible for the observed ion channel activity which may attenuate the infectivity. Missense mutations in the E protein which inhibited ion channel activity engendered attenuation [7,8]. It is reported that TMD forms stable pentamers and is confirmed by the molecular simulation and in vitro oligomerization [9]. It is reported that mutation of the hydrophobic amino acid residues in the TMD of the E protein with charged amino acids significantly alter the migrating properties of the E protein [3]. Analysis by Y. Liao et al. (2006) established that the TMD is essential for the membrane permeabilizing activity of the protein and also delineates that any missense mutations in the TMD of the E protein disrupt the function of the protein [3]. It is found that the envelope protein of SARS-CoV as well as SARS-CoV-2 contains three cysteine residues at positions 40, 43, and 44 respectively [10]. The first and third cysteine residues, at amino acid positions 40 and 44, respectively, were previously reported to play roles in oligomerization of the E protein [11]. Furthermore, from bio-chemical characterization it was learned that it undergoes translational modification by palmitoylation on all three cysteine residues [12]. Again, it may be noted from mutagenesis studies that the transmembrane domain is responsible for the membrane permeabilizing activity of the SARS-CoV E protein [13]. The (C)-terminal domain of envelope protein in SARS-CoV-2 binds to human PALS1, a tight junction-associated protein, which is essential for the establishment and maintenance of epithelial polarity in mammals [14].
Almost all the proteins embedded in the SARS-CoV-2 are being mutating as evidenced over the past few months [[15], [16], [17]]. It is hard to infer whether the mutations in E protein infect and sicken people deferentially due to COVID-19. In order to comprehend the effect of mutation over various proteins, one needs to accumulate all the mutations over the proteins from a large number of SARS-CoV-2 genomes available worldwide. On the other hand, most unsettled, controversial issue is the source/proximal origin of the SARS-CoV-2. Pattern of the genetic differences and motifs of the proteins present in SARS-CoV-2 distinguish it from any other known coronavirus E protein [18,19]. Zhang, Wu et al. (2020) showed that the natural reservoirs of SARS-CoV-2 are Bat and Pangolin [20]. Recently, based on genomic and protein sequences from few coronoviruses of different hosts including human, it was reported that Pangolin may not be intermediate host for coronavirus transmission from bat to human [21]. Presently, we wish to transact the transmission issue by analyzing mutations in one of most conserved proteins ( E protein) over the SARS-CoV-2 and other host-CoV genomes.
In this study, using protein sequences from a large number of coronaviruses from different hosts including human, we analyzed the phylogenetic relationship among them. A comparative investigation of the envelope (E) protein of CoVs of the β-genus family including SARS-CoV-2 from the perspective of missense mutations as well as molecular organization of the amino acids in the envelope proteins has been performed in order to gain an insight and discover the intermediate hosts.
2. Materials and methods
This study considered all the envelope proteins of coronaviruses from different hosts viz. Bat, Camel, Cat, Cattle, Pangolin, Chimpanzee and human SARS-CoV-2. In the Table 1 , total number of available CoV genomes of respective hosts as well as distinct numbers of envelope proteins in them are presented. (See Table 2.)
Table 1.
Envelope protein of different host-CoVs.
| Host | Total | Distinct | % of Variability of the E protein |
|---|---|---|---|
| Bat | 79 | 25 | 31.646% |
| Camel | 269 | 9 | 3.346% |
| Cat | 42 | 17 | 40.476% |
| Cattle | 22 | 2 | 9.090% |
| Pangolin | 1 | 1 | 0% |
| Chimpanzee | 1 | 1 | 0% |
| SARS-CoV2 | 4917 | 19 | 0.3864% |
Table 2.
List of distinct envelope (E) proteins from different host CoVs and their respective protein ID.
| Protein ID | Host | Protein ID | Host | Protein ID | Host |
|---|---|---|---|---|---|
| AIA62357 | Bat-CoV | AIA62302 | Bat-CoV | ADO39821 | Feline-CoV |
| AIA62348 | Bat-CoV | AVP78044 | Bat-CoV | ACT10858 | Feline-CoV |
| AHY61342 | Bat-CoV | AVI15004 | Bovine-CoV | ACT10869 | Feline-CoV |
| ASL68958 | Bat-CoV | AVZ61113 | Bovine-CoV | ACT10909 | Feline-CoV |
| ASL68947 | Bat-CoV | ALA50082 | Camel-CoV | ACT10941 | Feline-CoV |
| ATQ39391 | Bat-CoV | QCI31474 | Camel-CoV | ACT10974 | Feline-CoV |
| AUM60029 | Bat-CoV | QBM11741 | Camel-CoV | ACT10920 | Feline-CoV |
| QDF43841 | Bat-CoV | ASU89926 | Camel-CoV | AWW13513 | Chimpanzee-CoV |
| YP_009072442 | Bat-CoV | ASU90554 | Camel-CoV | QIG55947 | Pangolin CoV |
| YP_009273007 | Bat-CoV | ANI69894 | Camel-CoV | QHZ00381 | Human-SARS-CoV-2 |
| ABD75324 | Bat-CoV | ALA49346 | Camel-CoV | QKI36855 | Human-SARS-CoV-2 |
| AGC74167 | Bat-CoV | ALA49390 | Camel-CoV | QKG87268 | Human-SARS-CoV-2 |
| AKZ19089 | Bat-CoV | ASU90334 | Camel-CoV | QKE45838 | Human-SARS-CoV-2 |
| ADK66843 | Bat-CoV | QDM36990 | Feline-CoV | QJR88103 | Human-SARS-CoV-2 |
| QDF43816 | Bat-CoV | AYF53097 | Feline-CoV | YP_009724392 | Human-SARS-CoV-2 |
| ATO98160 | Bat-CoV | AXE71624 | Feline-CoV | QKI36831 | Human-SARS-CoV-2 |
| ATO98184 | Bat-CoV | ASU62492 | Feline-CoV | QJS53352 | Human-SARS-CoV-2 |
| QDF43821 | Bat-CoV | ASU62503 | Feline-CoV | QJA42107 | Human-SARS-CoV-2 |
| ATO98135 | Bat-CoV | AUG98123 | Feline-CoV | QJQ84210 | Human-SARS-CoV-2 |
| AHX37560 | Bat-CoV | AMD11134 | Feline-CoV | QJR89447 | Human-SARS-CoV-2 |
| AIA62280 | Bat-CoV | AGT52084 | Feline-CoV | QJI54124 | Human-SARS-CoV-2 |
| ABD75313 | Bat-CoV | AEK25514 | Feline-CoV | QKU31207 | Human-SARS-CoV-2 |
| AIA62312 | Bat-CoV | AEK25525 | Feline-CoV | QKU37035 | Human-SARS-CoV-2 |
| QKV07065 | Human-SARS-CoV-2 | ||||
| QKU32371 | Human-SARS-CoV-2 | ||||
| QKU28584 | Human-SARS-CoV-2 | ||||
| QKU52835 | Human-SARS-CoV-2 | ||||
| QKV06741 | Human-SARS-CoV-2 |
From the NCBI virus database, all the protein sequences of 4917 complete SARS-CoV-2 genomes as on date 18th June 2020 as well as other host CoV genomes were fetched. Then the amino acid sequences of envelope protein of all the CoVs from different hosts viz. Bat, Cat, Cattle, Pangolin, Chimpanzee, Human, are exported in fasta format using file management operations through MATLAB ver. R2020a [22]. The following is the complete list of seventy-four distinct envelope (E) proteins from different host CoVs and their respective protein IDs (Table-2).
Amino Acid Conservation Shannon Entropy: For each E protein, Shannon entropy of amino acid conservation over the amino acid sequence of E protein is computed using the following formula [23]:
For a given amino acid sequence of E protein of length l, the conservation of amino acids is calculated as follows:
where ; k i represents the number of occurrences of an amino acid s i in the given sequence.
3. Results
3.1. Mutations in the E protein of CoVs
It is noted that the envelope (E) protein of the CoVs of Pangolin and Chimpanzee are found to be 100% conserved as presented in Table 1 and consequently no mutation was found over there. In order to detect the missense mutations, we have made the multiple sequence alignment of the E protein sequences (Table-3) using the Clustal-Omega server [24,25]. In the following Table 4, description of the amino acid residues and their respective color and property are mentioned. These notations are also used in Fig. 2, 3, 4, 5 and 6
Table 4.
Amino acid residues and their respective color and property used in Fig. 2.
| Residue | Color | Property |
|---|---|---|
| A,V,F,P,M,I,L and W | RED | hydrophobic (incl.aromatic —Y) |
| D and E | BLUE | Acidic |
| Rand K | MAGENTA | Basic - H |
| S,T,Y,H,C,N,G and Q | GREEN | Hydroxyl + sulfhydryl + amine + G |
Fig. 2.
Sequence alignment of the E protein of Bat CoV.
It may be noted that an * (asterisk) indicates positions which have a single, fully conserved residue. Colon (:) indicates conservation between groups of strong similarity. Period (.) indicates conservation between groups of weak similarity [25].
3.1.1. Missense mutations of the E protein of bat CoV
Among 79 available complete CoV genomes of Bat, twenty-five unique sequences possess various mutations in the three domains of the E protein as presented in the Fig. 2.
The missense mutations over the E proteins of Bat-CoV with the respective domains are described in the Table 5. There exists variety of mutations in the envelope proteins of Bat-CoV.
Table 5.
Missense mutations in the envelope protein of the Bat CoV.
The most of the frame-shift mutations occurred in the C-terminal domain of the protein. There are also mutations in other two domains viz. TMD and N-terminal. Clearly, changes in the R-group property from Hydrophobic/Acidic to Hydrophilic/Basic of the amino acid residues of the three domains of the E protein may affect the function of the envelope protein. It is to be noted that envelope protein sequence of the protein QDF43841, YP_009273007, AIA62348 and ATQ39391 possess mutations at the cysteine residue such as C40V, C40I, C44V, C44I respectively. E protein sequence of the proteins AIA62357, ASL68958, AHY61342, AUM60029 contain the mutation C44A. These missense mutations at the cysteine residue may affect virus growth, release, entry, protein transport, and stability [26]. There is an important mutation V25C which is found in the TMD of E protein in the genome YP_009273007, which might stop the ion channel activity and led to in vivo attenuation. The TMD of the E protein for Bat CoV genomes AIA62348, ASL68947, AIA62357, ASL68958, ATQ39391 contains a mutation F26T and it may also cause stopping the ion channel activity [[27], [28], [29]]. Mutations in the motif"DFLV" might also affect its binding to the PALS1 protein and accordingly may influence replication and/or infectivity of the virus [30].
3.1.2. missense mutations of the E protein from camel CoV
Among 269 available complete CoV genomes of Camel, only 9 of them possess mutations as presented in the Fig. 3 .
Fig. 3.
Sequence alignment of the E protein of Camel CoV.
Most of the envelope proteins of the Camel CoV do not contain any mutations, only nine E proteins among the 269 Camel-CoV genomes possess few mutations. The envelope (E) protein possesses only three missense mutations viz. F17S in TMD of the protein ALA49346, S64L and D79H in C-terminal of the proteins QBM11741 and ANI69894 respectively. It is to be noted that the motif is '′DEWV′′ in the C-terminal end is absolutely conserved within the host-CoV except in ANI69894.
3.1.3. Missense mutations of the E protein of cat CoV
The highest amount (40.476%) of variability among the E proteins is found in the case of Cat-CoV although the mutations over the sequences is limited to seven different positions with 8.536% over the three domains as presented in the Fig. 4 .
Fig. 4.
Sequence alignment of the E protein of Cat CoV.
These missense mutations over TMD and C-terminal domains of the envelope protein of Cat CoV are shown in Table 6. It is worth noting that though the amount of variability of E proteins is too high comparatively, but the N-terminal of each E protein is absolutely conserved.
Table 6.
Missense mutation of the envelope protein of the Cat CoV.
The mutations in the TMD and C-terminal in the E protein across the Cat CoV would possibly affect the functions of the protein. The mutations in the TMD of the E protein would impact on ion channel activity of the envelope protein in the Cat CoV.
3.1.4. Missense mutations of the E protein of cattle CoV
Among 22 available complete CoV genomes of Cattle, only two of them had variations due with frame-shifts as shown in Fig. 5 .
Fig. 5.
Sequence alignment of the E protein of Cattle CoV.
The envelope proteins of the cattle CoV are highly conserved as shown in Fig. 5. It is noted that there are two frame-shifts in the N-terminal sequence.
3.1.5. Missense mutations of the E protein of human SARS-CoV-2
The E protein is present over all the available 4917 SARS-CoV-2 genomes as on 18th June 2020 in the NCBI database. There are only sixteen distinct E proteins over the 4917 available SARS-CoV-2 genomes. The mutations of the E proteins (presented in Table 7) are determined through the multiple sequence alignment as shown in Fig. 6 . It is to be noted that the mutations in the C-terminal domain of E protein from SARS-CoV to SARS-CoV-2 is already described in the unpublished article [31].
Table 7.
Protein ID and respective location of mutation of the E proteins over SARS-CoV-2.
| Protein ID and Respective Geo-location | Mutations | Domain | R-Group |
|---|---|---|---|
| QKO24093 (USA: San Diego, California) | E8K | N-terminal | Acidic to Basic |
| QKU52835 (USA: WA) | E7Q | N-terminal | Acidic to Basic |
| QKN20885 (USA), QJQ84210 (USA: New Orleans, LA) | F26L | TMD | Hydrophobic to Hydrophobic |
| QKI36831 (China: Guangzhou) | D72Y | C-terminal | Hydrophilic to Hydrophobic |
| QKI36855 (China: Guangzhou) | S68C | C-terminal | Hydrophilic to Hydrophobic |
| QKG87268, QKG88576 (USA: Massachusetts) | S68F | C-terminal | Hydrophilic to Hydrophobic |
| QKE45838 (USA:CA), QKE45886 (USA:CA) | P71L | C-terminal | Hydrophobic to Hydrophobic |
| QKE45898 (USA:CA), QKE45910 (USA:CA) | P71L | C-terminal | Hydrophobic to Hydrophobic |
| QJE38284 (USA:CA), QIU81527 (USA:WA), QKV06741 (USA: WA) | P71L | C-terminal | Hydrophobic to Hydrophobic |
| QKU32371 (USA: CA) | P71L | C-terminal | Hydrophobic to Hydrophobic |
| QJS53352 (Greece: Athens) | L39M | TMD | Hydrophobic to Hydrophobic |
| QJR88103 (Australia: Victoria) | L73F | C-terminal | Hydrophobic to Hydrophobic |
| QJA42107 (USA: VA) | A36V | TMD | Hydrophobic to Hydrophobic |
| QHZ00381 (South Korea) | L37H | TMD | Hydrophobic to Hydrophilic |
| QKU31207 (USA: CA) | T9I | TMD | Hydrophilic to Hydrophobic |
| QKU37035 (Saudi Arabia: Jeddah) | L19F | TMD | Hydrophobic to Hydrophobic |
| QKV07065 (USA: WA) | S55F | C-terminal | Hydrophilic to Hydrophobic |
| QKU28584 (USA: WA) | A41S | C-terminal | Hydrophobic Hydrophilic |
Fig. 6.
Sequence alignment of the E protein of SARS-CoV-2.
Most of the missense mutation occurred in the C-terminal. The E protein of QKN20885 (USA) and QJQ84210 (USA: New Orleans, LA) have a mutation at F26L in the TMD of the E protein. This particular mutation in the TMD terminate the ion channel activity and may led to in vivo attenuation. The E protein of QJS53352 (Greece: Athens), QJA42107 (USA: VA) and QHZ00381 (South Korea) contain mutations L39M, A36V and L37H respectively in the TMD of the E protein. These mutations in the TMD terminates the ion channel activity and led to in vivo attenuation. Several mutations have been found in the C-terminal of E proteins of SARS-CoV-2 and some of these mutations lead to non-synonymous R-group properties of amino acids, which might affect interaction of E protein with host proteins.
From the mutation data of different host-CoVs, it is concluded that the mutations over the E proteins of the SARS-CoV-2, Pangolin CoVs and Bat CoVs are almost similar in nature. It is to be mentioned that the SARS-CoV-2 E protein is much closer to that of the Pangolin-CoV, from the variability perspective. This closeness is also supported by sequence based homology. Here we illustrate the phylogenetic relationship among the E proteins ( Table 3 ) across different CoVs based on sequence homology, as shown in Fig. 7 .
Table 3.
Envelope proteins across different host CoVs.
| Host-CoVs | E protein sequence (N to C terminal of protein) | Length |
|---|---|---|
| Human SARS-CoV2 | MYSFVSEETGTLIVNSVLLFLAFVVFLLVTLAILTALRLCAYCCNIVNVSLVKPSFYVYSRVKNLNSSRVPDLLV | 75 |
| Chimpanzee-CoV | MFMADAYLADTVWYVGQIIFIVAICLLVTIVVVAFLATFKLCIQLCGMCNTLVLSPSIYVFNRGRQFYEFYNDIKPPVLDVDDV | 84 |
| Pangolin-CoV | MYSFVSEETGTLIVNSVLLFLAFVVFLLVTLAILTALRLCAYCCNIVNVSLVKPSFYVYSRVKNLNSSRVPDLLV | 75 |
| Feline or Cat-CoV | MMFPRAFTIIDDHGMVVSVFFWLLLIIILILFSIALLNVIKLCMVCCNLGKTIIVLPARHAYDAYKNFMHIKAYDPDEAFLV | 82 |
| Camel-CoV | MLPFVQERIGLFIVNFFIFTVVCAITLLVCMAFLTATRLCVQCITGFNTLLVQPALYLYNTGRSVYVKFQDSKPPLPPDEWV | 82 |
| Cattle or Bovine-CoV | MFMADAYFADTVWYVGQIIFIVAICLLVIIVVVAFLATFKLCIQLCGMCNTLVLSPSIYVFNRGRQFYEFYNDVKPPVLDVDDV | 84 |
| Bat-CoV | MYSFVSEETGTLIVNSVLLFLAFVVFLLVTLAILTALRLCAYCCNIVNVSLVKPTVYVYSRVKNLNSSEGVPDLLV | 76 |
Fig. 7.
Sequence homology based phylogeny of the envelope protein of different host-CoVs.
From the phylogeny Fig. 7, it is derived that among all E proteins of all the host CoVs, the E proteins of Pangolin-CoV and SARS-CoV-2 are very much close to each other. In order to get a more intensive phylogenetic relationship among the E proteins of the host CoVs, we further did amino acid frequency based phylogeny. We determined the amino acid frequencies for each of the common E proteins from each of the host CoV as tabulated in Table 8. Based on the frequency vector for each E protein, pairwise euclidean distance has been calculated and consequently the phylogeny is derived (Fig. 8 ).
Table 8.
Amino acid counts over the envelope proteins over the different host CoVs.
| Host-CoVs | A | R | N | D | C | Q | E | G | H | I | L | K | M | F | P | S | T | W | Y | V |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| SARS-CoV-2 | 4 | 3 | 5 | 1 | 3 | 0 | 2 | 1 | 0 | 3 | 14 | 2 | 1 | 5 | 2 | 8 | 4 | 0 | 4 | 13 |
| Chimpanzee-CoV | 6 | 2 | 3 | 6 | 4 | 3 | 1 | 3 | 0 | 8 | 9 | 2 | 3 | 7 | 3 | 2 | 4 | 1 | 5 | 12 |
| Pangolin-CoV | 4 | 3 | 5 | 1 | 3 | 0 | 2 | 1 | 0 | 3 | 14 | 2 | 1 | 5 | 2 | 8 | 4 | 0 | 4 | 13 |
| Cat-CoV | 7 | 2 | 3 | 5 | 3 | 0 | 1 | 2 | 3 | 11 | 11 | 4 | 5 | 7 | 3 | 2 | 2 | 1 | 3 | 7 |
| Camel-CoV | 4 | 3 | 3 | 2 | 4 | 4 | 2 | 3 | 0 | 5 | 11 | 2 | 2 | 8 | 6 | 2 | 7 | 1 | 3 | 10 |
| Bovine-CoV | 6 | 2 | 3 | 6 | 4 | 3 | 1 | 3 | 0 | 8 | 8 | 2 | 3 | 8 | 3 | 2 | 3 | 1 | 5 | 13 |
| Bat-CoV | 4 | 2 | 5 | 1 | 3 | 0 | 3 | 2 | 0 | 3 | 14 | 2 | 1 | 4 | 2 | 7 | 5 | 0 | 4 | 14 |
Fig. 8.
Phylogenetic relationship among the different host CoVs with respect to the amino acids conservation the envelope protein.
From the amino acid frequency based phylogeny, it is reconfirmed that the E protein of BatCoV and SARS-CoV-2 are co-evolved from the same origin. Further it is also confirmed that the E protein of Pangolin-CoV and SARS-CoV-2 are very much conserved from the point of amino acid conservation in the protein. It is worth mentioning that the Chimpanzee-CoV and Bovine-CoV contain the most closest E proteins as confirmed from the sequence based homology as well as amino acid conservation.
3.2. Phylogeny of the envelope proteins of host-CoVs
The sequence based homology of 74 distinct E proteins across the different host CoVs are presented in Fig. 9 .
Fig. 9.
Phylogenetic relationship among envelope proteins of the different host CoVs with respect to the sequence based homology.
The E proteins of the Bat-CoV, Pangolin-CoV and SARS-CoV-2 belong to the left hand side of the cladogram (from root) exclusively as shown in Fig. 9. The other side contains the E proteins of the other host CoVs. It is also observed that all the sixteen different E proteins of SARS-CoV-2 and that of Pangolin belong to a nearby neighbourhood.
In Table 9, for each of the E proteins of the CoVs, frequency of each amino acids is computed, which yields the amino acids conservation based phylogeny (Fig. 10 ).
Table 9.
Frequency of amino acids over the envelope proteins across the seven different host-CoVs.
| Name | Host | A | R | N | D | C | Q | E | G | H | I | L | K | M | F | P | S | T | W | Y | V |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ASL68947 | Bat CoV | 7 | 2 | 3 | 1 | 4 | 5 | 3 | 3 | 0 | 6 | 8 | 2 | 3 | 7 | 6 | 3 | 6 | 1 | 3 | 9 |
| ASU90554 | Camel CoV | 4 | 3 | 3 | 2 | 4 | 3 | 2 | 3 | 1 | 4 | 11 | 2 | 3 | 8 | 6 | 2 | 7 | 1 | 3 | 10 |
| ASL68958 | Bat CoV | 7 | 2 | 2 | 1 | 4 | 5 | 3 | 3 | 0 | 7 | 8 | 2 | 3 | 7 | 6 | 3 | 6 | 1 | 3 | 9 |
| ANI69894 | Camel CoV | 4 | 3 | 3 | 1 | 4 | 4 | 2 | 3 | 1 | 4 | 11 | 2 | 3 | 8 | 6 | 2 | 7 | 1 | 3 | 10 |
| AXE71624 | Feline CoV | 7 | 2 | 4 | 4 | 3 | 1 | 1 | 2 | 2 | 11 | 10 | 3 | 5 | 7 | 3 | 3 | 3 | 1 | 3 | 7 |
| ALA49346 | Camel CoV | 4 | 3 | 3 | 2 | 4 | 4 | 2 | 3 | 0 | 4 | 11 | 2 | 3 | 7 | 6 | 3 | 7 | 1 | 3 | 10 |
| AGT52084 | Feline CoV | 7 | 2 | 3 | 4 | 3 | 1 | 1 | 2 | 2 | 11 | 11 | 4 | 5 | 6 | 3 | 3 | 3 | 1 | 3 | 7 |
| AUM60029 | Bat CoV | 6 | 2 | 3 | 1 | 4 | 6 | 2 | 3 | 0 | 6 | 8 | 2 | 3 | 7 | 6 | 3 | 5 | 1 | 3 | 11 |
| ACT10909 | Feline CoV | 7 | 3 | 3 | 4 | 3 | 1 | 1 | 2 | 2 | 10 | 11 | 3 | 6 | 6 | 3 | 2 | 3 | 1 | 3 | 8 |
| AHY61342 | Bat CoV | 7 | 2 | 3 | 1 | 4 | 5 | 3 | 3 | 0 | 7 | 9 | 2 | 2 | 7 | 6 | 3 | 4 | 1 | 3 | 10 |
| AIA62348 | Bat CoV | 7 | 2 | 2 | 1 | 5 | 4 | 3 | 3 | 3 | 6 | 8 | 1 | 1 | 6 | 6 | 3 | 4 | 1 | 3 | 13 |
| ACT10941 | Feline CoV | 7 | 2 | 3 | 4 | 3 | 1 | 1 | 3 | 2 | 11 | 12 | 4 | 5 | 6 | 3 | 2 | 3 | 1 | 3 | 6 |
| AYF53097 | Feline CoV | 7 | 2 | 3 | 4 | 3 | 1 | 1 | 2 | 2 | 10 | 11 | 4 | 5 | 7 | 3 | 2 | 3 | 1 | 3 | 8 |
| QCI31474 | Camel CoV | 4 | 3 | 3 | 2 | 4 | 4 | 2 | 3 | 0 | 4 | 11 | 2 | 3 | 8 | 6 | 2 | 7 | 1 | 3 | 10 |
| ASU62492 | Feline CoV | 7 | 2 | 3 | 4 | 3 | 1 | 1 | 2 | 2 | 11 | 11 | 4 | 5 | 7 | 3 | 2 | 3 | 1 | 3 | 7 |
| ACT10974 | Feline CoV | 6 | 2 | 3 | 4 | 3 | 1 | 1 | 2 | 2 | 11 | 11 | 4 | 5 | 7 | 3 | 2 | 3 | 1 | 3 | 8 |
| ALA49390 | Camel CoV | 4 | 3 | 3 | 2 | 4 | 4 | 2 | 3 | 0 | 4 | 12 | 2 | 3 | 7 | 6 | 2 | 7 | 1 | 3 | 10 |
| ASU89926 | Camel CoV | 4 | 3 | 3 | 2 | 4 | 4 | 2 | 3 | 0 | 5 | 11 | 2 | 2 | 8 | 6 | 2 | 7 | 1 | 3 | 10 |
| ACT10869 | Feline CoV | 7 | 1 | 3 | 4 | 4 | 1 | 1 | 3 | 2 | 11 | 12 | 4 | 5 | 6 | 3 | 2 | 3 | 1 | 3 | 6 |
| AIA62357 | Bat CoV | 6 | 3 | 5 | 1 | 4 | 3 | 3 | 3 | 1 | 8 | 8 | 1 | 1 | 8 | 6 | 1 | 6 | 1 | 3 | 10 |
| ASU90334 | Camel CoV | 4 | 3 | 3 | 2 | 4 | 4 | 2 | 3 | 0 | 4 | 11 | 2 | 2 | 8 | 6 | 2 | 7 | 1 | 3 | 10 |
| ASU62503 | Feline CoV | 7 | 2 | 3 | 4 | 3 | 1 | 1 | 2 | 2 | 11 | 12 | 4 | 5 | 6 | 3 | 2 | 3 | 1 | 3 | 7 |
| ADO39821 | Feline CoV | 7 | 2 | 2 | 5 | 3 | 1 | 1 | 2 | 2 | 11 | 11 | 4 | 5 | 7 | 3 | 2 | 3 | 1 | 3 | 7 |
| QDM36990 | Feline CoV | 7 | 2 | 4 | 4 | 3 | 1 | 1 | 2 | 2 | 11 | 11 | 4 | 4 | 7 | 3 | 2 | 2 | 1 | 3 | 8 |
| ACT10858 | Feline CoV | 7 | 2 | 4 | 4 | 3 | 1 | 1 | 2 | 2 | 11 | 12 | 4 | 5 | 6 | 3 | 2 | 2 | 1 | 3 | 7 |
| AWW13513 | Chimpanzee CoV | 6 | 2 | 3 | 6 | 4 | 3 | 1 | 3 | 0 | 8 | 9 | 2 | 3 | 7 | 3 | 2 | 4 | 1 | 5 | 12 |
| ACT10920 | Feline CoV | 7 | 2 | 4 | 4 | 3 | 1 | 1 | 2 | 2 | 11 | 11 | 3 | 5 | 7 | 2 | 2 | 2 | 1 | 3 | 7 |
| ATQ39391 | Bat CoV | 4 | 2 | 3 | 0 | 4 | 5 | 4 | 3 | 0 | 5 | 8 | 2 | 3 | 7 | 6 | 3 | 7 | 1 | 3 | 12 |
| QBM11741 | Camel CoV | 4 | 3 | 3 | 2 | 4 | 4 | 2 | 3 | 0 | 4 | 12 | 2 | 3 | 8 | 6 | 1 | 7 | 1 | 3 | 10 |
| AVI15004 | Bovine CoV | 6 | 2 | 3 | 6 | 4 | 3 | 1 | 3 | 0 | 8 | 8 | 2 | 3 | 8 | 3 | 2 | 3 | 1 | 5 | 13 |
| AUG98123 | Feline CoV | 7 | 3 | 3 | 4 | 3 | 0 | 1 | 2 | 2 | 12 | 11 | 4 | 5 | 7 | 3 | 2 | 3 | 1 | 3 | 6 |
| AMD11134 | Feline CoV | 7 | 2 | 3 | 5 | 3 | 0 | 1 | 2 | 3 | 11 | 11 | 4 | 5 | 7 | 3 | 2 | 2 | 1 | 3 | 7 |
| AEK25525 | Feline CoV | 7 | 2 | 3 | 4 | 3 | 0 | 1 | 2 | 2 | 11 | 11 | 5 | 5 | 7 | 3 | 2 | 3 | 1 | 3 | 7 |
| AVZ61113 | Bovine CoV | 6 | 2 | 3 | 6 | 4 | 3 | 1 | 3 | 0 | 8 | 8 | 2 | 2 | 7 | 3 | 2 | 3 | 1 | 5 | 13 |
| ALA50082 | Camel CoV | 6 | 2 | 3 | 6 | 4 | 3 | 1 | 3 | 0 | 9 | 8 | 2 | 2 | 8 | 3 | 2 | 3 | 1 | 5 | 13 |
| AEK25514 | Feline CoV | 7 | 2 | 3 | 4 | 3 | 1 | 1 | 2 | 2 | 11 | 12 | 4 | 5 | 7 | 3 | 2 | 3 | 0 | 3 | 7 |
| YP_009072442 | Bat CoV | 6 | 3 | 3 | 1 | 4 | 5 | 3 | 3 | 0 | 5 | 12 | 1 | 1 | 4 | 2 | 3 | 5 | 0 | 5 | 13 |
| QDF43841 | Bat CoV | 3 | 1 | 5 | 2 | 5 | 2 | 5 | 4 | 1 | 10 | 15 | 2 | 1 | 5 | 1 | 4 | 3 | 0 | 2 | 10 |
| YP_009273007 | Bat CoV | 2 | 0 | 3 | 2 | 6 | 2 | 4 | 2 | 0 | 7 | 12 | 3 | 1 | 4 | 1 | 5 | 6 | 0 | 4 | 12 |
| QHZ00381 | SARS-CoV-2 | 4 | 3 | 5 | 1 | 3 | 0 | 2 | 1 | 1 | 3 | 13 | 2 | 1 | 5 | 2 | 8 | 4 | 0 | 4 | 13 |
| ATO98135 | Bat CoV | 4 | 2 | 5 | 1 | 3 | 1 | 2 | 2 | 0 | 3 | 14 | 2 | 1 | 4 | 2 | 7 | 5 | 0 | 4 | 14 |
| AIA62302 | Bat CoV | 4 | 2 | 5 | 2 | 4 | 0 | 2 | 1 | 0 | 3 | 12 | 2 | 2 | 4 | 2 | 7 | 5 | 0 | 4 | 15 |
| QJS53352 | SARS-CoV-2 | 4 | 3 | 5 | 1 | 3 | 0 | 2 | 1 | 0 | 3 | 13 | 2 | 2 | 5 | 2 | 8 | 4 | 0 | 4 | 13 |
| QDF43816 | Bat CoV | 4 | 2 | 5 | 1 | 3 | 0 | 3 | 2 | 0 | 4 | 14 | 2 | 1 | 4 | 2 | 7 | 5 | 0 | 4 | 13 |
| ABD75324 | Bat CoV | 4 | 2 | 5 | 1 | 3 | 0 | 3 | 2 | 0 | 3 | 13 | 2 | 1 | 5 | 2 | 7 | 5 | 0 | 4 | 14 |
| ADK66843 | Bat CoV | 4 | 2 | 4 | 0 | 3 | 1 | 4 | 1 | 0 | 3 | 13 | 2 | 1 | 6 | 2 | 8 | 5 | 0 | 4 | 13 |
| ATO98160 | Bat CoV | 5 | 2 | 5 | 1 | 3 | 0 | 3 | 2 | 0 | 3 | 14 | 2 | 1 | 4 | 2 | 6 | 5 | 0 | 4 | 14 |
| AIA62280 | Bat CoV | 5 | 2 | 5 | 1 | 3 | 0 | 3 | 2 | 0 | 3 | 13 | 2 | 1 | 4 | 2 | 6 | 5 | 0 | 4 | 15 |
| QJR88103 | SARS-CoV-2 | 4 | 3 | 5 | 1 | 3 | 0 | 2 | 1 | 0 | 3 | 13 | 2 | 1 | 6 | 2 | 8 | 4 | 0 | 4 | 13 |
| AKZ19089 | Bat CoV | 5 | 2 | 5 | 1 | 3 | 0 | 3 | 2 | 0 | 3 | 14 | 2 | 1 | 4 | 2 | 7 | 4 | 0 | 4 | 14 |
| QDF43821 | Bat CoV | 4 | 2 | 5 | 1 | 3 | 0 | 3 | 2 | 0 | 3 | 14 | 2 | 1 | 4 | 2 | 7 | 5 | 0 | 4 | 14 |
| QKI36855 | SARS-CoV-2 | 4 | 3 | 5 | 1 | 4 | 0 | 2 | 1 | 0 | 3 | 14 | 2 | 1 | 5 | 2 | 7 | 4 | 0 | 4 | 13 |
| AIA62312 | Bat CoV | 4 | 2 | 5 | 1 | 3 | 0 | 3 | 2 | 0 | 3 | 13 | 2 | 1 | 4 | 2 | 7 | 5 | 0 | 4 | 15 |
| ABD75313 | Bat CoV | 4 | 2 | 5 | 2 | 4 | 0 | 2 | 1 | 0 | 3 | 13 | 2 | 1 | 4 | 2 | 7 | 5 | 0 | 4 | 15 |
| QKG87268 | SARS-CoV-2 | 4 | 3 | 5 | 1 | 3 | 0 | 2 | 1 | 0 | 3 | 14 | 2 | 1 | 6 | 2 | 7 | 4 | 0 | 4 | 13 |
| AHX37560 | Bat CoV | 4 | 2 | 4 | 1 | 3 | 0 | 3 | 2 | 0 | 3 | 14 | 2 | 1 | 4 | 2 | 8 | 5 | 0 | 4 | 14 |
| AGC74167 | Bat CoV | 4 | 2 | 5 | 1 | 3 | 0 | 2 | 2 | 0 | 3 | 13 | 2 | 1 | 5 | 2 | 7 | 5 | 0 | 4 | 15 |
| AVP78044 | Bat CoV | 4 | 3 | 5 | 1 | 3 | 0 | 2 | 1 | 0 | 3 | 14 | 2 | 1 | 5 | 2 | 8 | 4 | 0 | 4 | 13 |
| QIG55947 | Pangolin CoV | 4 | 3 | 5 | 1 | 3 | 0 | 2 | 1 | 0 | 3 | 14 | 2 | 1 | 5 | 2 | 8 | 4 | 0 | 4 | 13 |
| YP_009724392 | SARS-CoV-2 | 4 | 3 | 5 | 1 | 3 | 0 | 2 | 1 | 0 | 3 | 14 | 2 | 1 | 5 | 2 | 8 | 4 | 0 | 4 | 13 |
| QJR89447 | SARS-CoV-2 | 4 | 3 | 5 | 1 | 3 | 0 | 2 | 1 | 0 | 3 | 14 | 2 | 1 | 5 | 2 | 8 | 4 | 0 | 4 | 12 |
| QJQ84210 | SARS-CoV-2 | 4 | 3 | 5 | 1 | 3 | 0 | 2 | 1 | 0 | 3 | 15 | 2 | 1 | 4 | 2 | 8 | 4 | 0 | 4 | 13 |
| QJA42107 | SARS-CoV-2 | 3 | 3 | 5 | 1 | 3 | 0 | 2 | 1 | 0 | 3 | 14 | 2 | 1 | 5 | 2 | 8 | 4 | 0 | 4 | 14 |
| ATO98184 | Bat CoV | 4 | 2 | 5 | 1 | 3 | 0 | 3 | 2 | 0 | 3 | 15 | 2 | 1 | 4 | 1 | 7 | 5 | 0 | 4 | 14 |
| QKE45838 | SARS-CoV-2 | 4 | 3 | 5 | 1 | 3 | 0 | 2 | 1 | 0 | 3 | 15 | 2 | 1 | 5 | 1 | 8 | 4 | 0 | 4 | 13 |
| QKI36831 | SARS-CoV-2 | 4 | 3 | 5 | 0 | 3 | 0 | 2 | 1 | 0 | 3 | 14 | 2 | 1 | 5 | 2 | 8 | 4 | 0 | 5 | 13 |
| QJI54124 | SARS-CoV-2 | 4 | 3 | 5 | 0 | 3 | 0 | 2 | 1 | 0 | 3 | 13 | 2 | 1 | 5 | 2 | 8 | 4 | 0 | 4 | 13 |
| QKU31207 | SARS-CoV-2 | 4 | 3 | 5 | 1 | 3 | 0 | 2 | 1 | 0 | 4 | 14 | 2 | 1 | 5 | 2 | 8 | 3 | 0 | 4 | 13 |
| QKU37035 | SARS-CoV-2 | 4 | 3 | 5 | 1 | 3 | 0 | 2 | 1 | 0 | 3 | 13 | 2 | 1 | 6 | 2 | 8 | 4 | 0 | 4 | 13 |
| QKV07065 | SARS-CoV-2 | 4 | 3 | 5 | 1 | 3 | 0 | 2 | 1 | 0 | 3 | 14 | 2 | 1 | 6 | 2 | 7 | 4 | 0 | 4 | 13 |
| QKU28584 | SARS-CoV-2 | 3 | 3 | 5 | 1 | 3 | 0 | 2 | 1 | 0 | 3 | 14 | 2 | 1 | 5 | 2 | 9 | 4 | 0 | 4 | 13 |
| QKU52835 | SARS-CoV-2 | 4 | 3 | 5 | 1 | 3 | 1 | 1 | 1 | 0 | 3 | 14 | 2 | 1 | 5 | 2 | 8 | 4 | 0 | 4 | 13 |
Fig. 10.
Phylogenetic relationship among envelope proteins of the different host CoVs with respect to the amino acids conservation.
From the sequence homology (Fig. 9) it is observed that the E proteins of AIA62312 and ABD75324 of Bat-CoV are very much close. Based on the amino acid conservation over the E protein, the phylogeny (Fig. 10) further showed that the E proteins of QDF43821, ATO98184, AHX37560, AGC74167, AKZ19089, AIA62280, ATO98160, ATO98135 of Bat-CoV are in the same branch with same level of the phylogeny. The phylogeny in Fig. 9 describes that the E proteins of QJR89447 and QJQ84210 of SARS-CoV2 are very close. It is obtained that the E proteins of AVP78044 (Bat-CoV), QIG55947 (Pangolin-CoV) and YP_009724392 (SARS-CoV-2) are close to that of QJR89447 (SARS-CoV-2) from the phylogeny based on amino acid conservations (Fig. 10). The E proteins of QKI36855, QJA42107, QKE45838, QKI36831 and QJI54124 of SARS-CoV2 are in the close proximity to that of the QJQ84210 (SARS-CoV-2) based on amino acid conservations. Again the E proteins of QKU31207 and YP_009724392 of SARS-CoV-2 are found to be near enough based on the homology based phylogeny.
It is observed that almost all the E proteins of SARS-CoV-2 as well as Bat and Pangolin-CoVs do not contain the amino acids tryptophan, glutamine and histidine. The E proteins of all the host CoVs are leucine and valine residues rich as observed in Table 10.
Table 10.
Shannon entropy of the amino acid conservation of the E protein of the host CoVs.
| Name | Host | SE | Name | Host | SE | Name | Host | SE |
|---|---|---|---|---|---|---|---|---|
| ASL68947 | Bat CoV | 0.933 | ACT10858 | Feline CoV | 0.919 | AIA62280 | Bat CoV | 0.851 |
| ASU90554 | Camel CoV | 0.932 | AWW13513 | Chimpanzee CoV | 0.918 | QJR88103 | SARS-CoV2 | 0.850 |
| ASL68958 | Bat CoV | 0.930 | ACT10920 | Feline CoV | 0.916 | QKU37035 | SARS-CoV2 | 0.850 |
| ANI69894 | Camel CoV | 0.929 | ATQ39391 | Bat CoV | 0.916 | AKZ19089 | Bat CoV | 0.850 |
| AXE71624 | Feline CoV | 0.928 | QBM11741 | Camel CoV | 0.915 | QDF43821 | Bat CoV | 0.850 |
| ALA49346 | Camel CoV | 0.927 | AVI15004 | Bovine CoV | 0.914 | QKI36855 | SARS-CoV2 | 0.850 |
| AGT52084 | Feline CoV | 0.926 | AUG98123 | Feline CoV | 0.912 | AIA62312 | Bat CoV | 0.849 |
| AUM60029 | Bat CoV | 0.926 | AMD11134 | Feline CoV | 0.912 | ABD75313 | Bat CoV | 0.848 |
| ACT10909 | Feline CoV | 0.926 | AEK25525 | Feline CoV | 0.912 | QKG87268 | SARS-CoV-2 | 0.848 |
| AHY61342 | Bat CoV | 0.925 | AVZ61113 | Bovine CoV | 0.912 | QKV07065 | SARS-CoV-2 | 0.848 |
| AIA62348 | Bat CoV | 0.925 | ALA50082 | Camel CoV | 0.909 | AHX37560 | Bat CoV | 0.847 |
| ACT10941 | Feline CoV | 0.924 | AEK25514 | Feline CoV | 0.908 | AGC74167 | Bat CoV | 0.847 |
| AYF53097 | Feline CoV | 0.924 | YP_009072442 | Bat CoV | 0.888 | AVP78044 | Bat CoV | 0.846 |
| QCI31474 | Camel CoV | 0.923 | QDF43841 | Bat CoV | 0.881 | QIG55947 | Pangolin CoV | 0.846 |
| ASU62492 | Feline CoV | 0.922 | YP_009273007 | Bat CoV | 0.868 | YP_009724392 | SARS-CoV-2 | 0.846 |
| ACT10974 | Feline CoV | 0.922 | QHZ00381 | SARS-CoV-2 | 0.862 | QKU31207 | SARS-CoV-2 | 0.846 |
| ALA49390 | Camel CoV | 0.921 | ATO98135 | Bat CoV | 0.858 | QJR89447 | SARS-CoV-2 | 0.843 |
| ASU89926 | Camel CoV | 0.921 | AIA62302 | Bat CoV | 0.857 | QKU28584 | SARS-CoV-2 | 0.842 |
| ACT10869 | Feline CoV | 0.920 | QJS53352 | SARS-CoV-2 | 0.856 | QJQ84210 | SARS-CoV-2 | 0.841 |
| AIA62357 | Bat CoV | 0.920 | QDF43816 | Bat CoV | 0.856 | QJA42107 | SARS-CoV-2 | 0.840 |
| ASU90334 | Camel CoV | 0.920 | ABD75324 | Bat CoV | 0.855 | ATO98184 | Bat CoV | 0.840 |
| ASU62503 | Feline CoV | 0.920 | ADK66843 | Bat CoV | 0.852 | QKE45838 | SARS-CoV2 | 0.836 |
| ADO39821 | Feline CoV | 0.920 | QKU52835 | SARS-CoV-2 | 0.852 | QKI36831 | SARS-CoV-2 | 0.835 |
| QDM36990 | Feline CoV | 0.919 | ATO98160 | Bat CoV | 0.851 | QJI54124 | SARS-CoV-2 | 0.824 |
Based on the amino acid frequency vector for each proteins, the Shannon entropy (SE) is computed which is tabulated in Table 10. This SE of the amino acid conservation of the E protein suggests molecular level closeness of the E protein.
From the Table 10, it is quite evident that the conservation of amino acids over the E protein of Bat-CoV is highly diverse as SE value is in the interval of 0.84 and 0.94 whereas SE of most common E protein of SARS-CoV-2 and that of the Pangolin-CoV are found to be identical and it is close to 0.846. Note that, there is an E protein of AVP78044 (Bat-CoV) whose SE is also identical to 0.846. The remaining fifteen different E proteins of SARS-CoV-2 are close enough to other Bat-CoVs by accumulating various missense mutations. The SE of the E protein of SARS-CoV2 lies in between 0.824 and 0.862. There are E proteins of SARS-CoV-2 whose SE of amino acid conservation is tightly bounded by that of Pangolin and Bat-CoVs. It is found that SE of E proteins of ADK66843 (Bat-CoV) and QKU52835 (SARS-CoV-2) are turned out to be identical (0.852). There are other such examples too which are clearly observed in the Table 10. This phylogenetic relationship is endorsed by the amino acid conservation and their associated SE found in Table 10. We also observed phylogenetic relationship among E proteins from Bat-CoV, Pangolin-CoV and SARS-CoV-2 (Fig. 11 ). This relationship was drawn using amino acid conservation and their associated SE (Table 10).
Fig. 11.
Phylogenetic relationship among envelope proteins of the SARS-CoV2, Bat and Pangolin CoVs with respect to the amino acids conservation.
4. Conclusions
Here, we performed phylogenetic analysis of E protein sequences of coronaviruses from different hosts although different investigators also performed phylogenetic analysis using the genomic and protein sequences of few coronaviruses from different hosts [21]. But the phylogenetic analysis, using E protein sequences from a large number of seuquences, may provide a better picture of the relationship among hosts coronaviruses so far as the intermediate host between human and bat is concerned since protein is the functional unit in the cell. So, this study, using protein sequence variations, may provide the clue why few hosts are resistant or sensitive to the disease Covid-19. We observed variations in protein sequences of E-protein in Human-SARS-CoV-2, Bat-CoV, Camel-CoV etc. Based on mutation characteristics and amino acid conservations over the E proteins across various host CoVs, this report predicts potential close kins of human SARS-CoV-2 as the Pangolin-CoV and Bat-CoV which was also reported in a recent study [21]. Pangolin, the closest kin of SARS-CoV-2, is also confirmed by the analysis made in this study. The missense mutations of the E protein across various host CoVs, may bar the usual functions of the envelope protein and consequently the virus may become weaker in infectivity. It is our belief that various missense mutations in the E protein could weaken the SARS-CoV-2 and would help us gets rid of COVID-19 in future since any virus does not like to destroy its host for its survival for a long to come.
Data availability
The protein sequences of the SARS-CoV-2 and other host CoVs used in this study are available in the NCBI virus database https : //www. ncbi. nlm. nih. gov/labs/virus/vssi/.
Author contributions
SH conceived the problem. SH determined the mutations. SH, PPC, BR analyzed the data and result. SH wrote the initial draft which was checked and edited by all other authors to generate the final version.
Declaration of Competing Interest
The authors do not have any conflicts of interest to declare.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
The protein sequences of the SARS-CoV-2 and other host CoVs used in this study are available in the NCBI virus database https : //www. ncbi. nlm. nih. gov/labs/virus/vssi/.