Table 3. List of class A GPCRs included in the study (continued from Tables 1, 2).
| Subgrp idx | # GPCRs in subgrp | GPCRs included in the subgroupsa | Natural ligand | Chemical class of natural ligandb | Notesc |
| 20 | 3 | TACR1 (NK1R), TACR1 (NK2R), TACR3 (NK3R) | tachykinin neuropeptides | peptide | |
| 21 | 3 | TSHR, LHCGR (LSHR), FSHR | glycoprotein hormones | peptide | |
| 22 | 4 | F2R (PAR1), F2RL1 (PAR2), F2RL2 (PAR3), F2RL3 (PAR4) | unmasked N-terminus | peptide | |
| 23 | 5 | GPR83, NPY1R, NPY2R, PPYR1 (NPY4R), NPY5R | neuropeptide Y and peptide YY | peptide | o |
| 24 | 3 | C3AR1 (C3AR), C5AR1 (C5AR), GPR77 (C5ARL) | anaphylatoxins | peptide | |
| 25 | 4 | EDNRA, EDNRB, GPR37, GPR37L1 (ETBR2) | Endothelins | peptide | o |
| 26 | 5 | LGR5, LGR6, RXFP1 (LGR7), RXFP2 (LGR8) | Relaxin | peptide | |
| 27 | 3 | GALR1, GALR2, GALR3 | Galanin | peptide | N |
| 28 | 4 | OPRL1 (OPRX), OPRM1 (OPRM), OPRD1 (OPRD), OPRK1 (OPRK) | opioid peptides | peptide | N |
| 29 | 3 | SSTR2 (SSR2), SSTR3 (SSR3), SSTR5 (SSR5) | somatostatins | peptide | |
| 30 | 3 | GRPR, NMBR, BRS3 | bombesin-related peptides | peptide | |
| 31 | 3 | MC3R, MC4R, MC5R | melanocortins | peptide | N |
| 32 | 3 | AVPR1A (V1AR), AVPR1B (V1BR), AVPR2 (V2R) | Vasopressin | peptide | N |
| 33 | 10 | CXCR1, CXCR2, CXCR3, CXCR4, CXCR5, CXCR6, CCR6, CCR7, CCR9, CCR10 | Chemokines | peptide | |
| 34 | 5 | APLNR (APJ), AGTR1 (AG2R, AG2S), RL3R1 (RLN3R2), RXFP4 (RLN3R2) | apelin (APLNR), angiotensin (AGTR1), relaxin (RL3R1, RLN3R2) | peptide | |
| 35 | 3 | NTSR1 (NTR1), NTSR2 (NTR2), GPR39 | neurotensin, obestatin (GPR39) | peptide | |
| 36 | 9 | CCR1, CCR2, CCR3, CCR4, CCR5, CCR8, CCRL2, CX3CR1(CX3CR1, C3X1), CCBP2 | Chemokines | peptide | S |
| 37 | 3 | FPR1, FPR2 (FPRL1), FPR3 (FPRL2) | N-formyl-methionyl peptides (FPRs) | peptide | |
| 38 | 4 | MRGPRX1 (MRGX1), MRGPRX2 (MRGX2), MRGPRX3 (MRGX3), MRGPRX4 (MRGX4) | enkephalins (MRGPRX1), cortistatins (MRGPRX2) | peptide | o |
a
The receptors are indicated through their gene name. Uniprot name, when different from the gene name, and common synonyms are listed in parentheses. Orphan receptors are indicated in bold and indicated as ‘o’ in Notes.
c
The Symbol “N” indicates that pairs of receptors of the subgroup do not satisfy max(d N)<1 in the Nei-Gojobori counting scheme [64]. The symbol “S” indicates that pairs of receptors from the subgroup do not satisfy max (d S)<3 in the Nei-Gojobori scheme. The symbol “o” indicates that the subgroup has one or more orphan GPCR.