Table 2.
Aquaporin isoforms examined for each aquaporin type and key observations from comparative sequence analysis*
| AQP Type | Organism | Observations from sequence alignment | |||
|---|---|---|---|---|---|
| Human | Mouse | Rat | Chicken | ||
| AQP1 | 2 | 1 | 1 | 1 | Human transcript ENST00000265298 lacked the first 94 amino acids of ENST00000311813 which is present in the AQP1 from mouse, rat and chicken. This N-terminal region of the sequence contained the first NPA motif. However, the second NPA motif starting at position 192 in ENST00000311813 is conserved in all the 5 protein sequences |
| AQP3 | 3 | 1 | 1 | 1 | Human transcript ENST00000379492 lacked the first 34 amino acids present in the other isoforms. |
| AQP4 | 3 | 2 | 2 | 2 | All the organisms had multiple transcripts. |
| AQP5 | 1 | 2 | 2 | 3 | The first NPA motif was observed in all the protein sequences. Two chicken transcripts ENSGALT00000041244 and ENSGALT00000041246 and two rodent transcripts ENSMUST00000088200 and ENSRNOT00000040874 produced isoforms that lacked the second NPA motif. |
| AQP7 | 4 | 3 | 1 | 1 | All nine protein sequences of AQP7 contained atypical water transport NPA motifs. The first motif is NAA while the second motif was NPS. |
| AQP8 | 1 | 2 | 1 | 1 | The first water-transport motif for chicken AQP8 was NPV |
| AQP9 | 1 | 4 | 1 | 2 | Except for mouse transcript ENSMUST00000113569, all other AQP9 protein sequences had the second NPA motif. |
| AQP11 | 1 | 2 | 2 | 1 | The first water transporting motif was atypical (NPC) in all the isoforms examined. Only three protein isoforms from transcripts ENSRNOT00000018091, ENSMUST00000084986 and ENST00000313578 contained the second NPA motif. |
| AQP12 | 2 | 1 | 1 | 1 | Human transcript ENST00000373309 lacked the first NPA-like motif (NPT) present in the other sequences. |
*Additional File 1 contains the multiple sequence alignment for AQP0 to AQP12. Ensembl Identifiers preceded by ENST, ENSMUST, ENSRNOT, and ENSGALT are for human, mouse, rat and chicken transcripts respectively.