Table 1. Multiple sequence alignment and location of human apelin and ELABELA, the endogenous peptide ligands of the apelin receptor.
| Name | Multiple sequence alignment | Location |
|---|---|---|
| Apelin-77 | MNLRLCVQALLLLWLSLTAVCGGSLMPLPDGNGLEDGNVRHLVQPRGSRNGPGPWQGGRRKFRRQRPRLSHKGPMPF | |
| Apelin-55 | ----------------------GSLMPLPDGNGLEDGNVRHLVQPRGSRNGPGPWQGGRRKFRRQRPRLSHKGPMPF | |
| Apelin-36 | -----------------------------------LVQPRGSRNGPGPWQGGRRKFRRQRPRLSHKGPMPF | Lung, testis and uterus (rat) |
| Apelin-17 | ---------------------------------------------------------------------KFRRQRPRLSHKGPMPF | Plasma |
| Pyr-apelin-13 | -------------------------------------------------------------------------Pyr-RPRLSHKGPMPF | Plasma,placental chorionic villi |
| Apelin-13 | ----------------------------------------------------------------------------QRPRLSHKGPMPF | plasma,mammary gland (rat) |
| Apelin-12 | ------------------------------------------------------------------------------RPRLSHKGPMPF | |
| ELABELA-54 | MRFQQFLFAFFIFIMSLLLISGQEPVNLTMRRKLRKHNCLQRRCMPLHSRVPFP- | |
| ELABELA-32 | ------------------------------------------QEPVNLTMRRKLRKHNCLQRRCMPLHSRVPFP- | Embryos, cardiac endothelium, blood vessels, kidney, prostate and placenta |
| ELABELA-22 | ------------------------------------KLRKHNC----------------------LQRRCMPLHSRVPFP- | |
| ELABELA-21 | --------------------------------------LRKHNC----------------------LQRRCMPLHSRVPFP- | |
| ELABELA-11 | -----------------------------------------------------------------------------CMPLHSRVPFP- *: *: * |
*, represents a consistent sequence;:, represents a homologous sequence; red, indicates the identical amino acid. From the sequence alignment, it can be seen that Leucine (L) and Proline (P) is the conserved amino acid, which may be the key amino acid for the binding of apelin and ELA to APJ. ELA, Elabela; APJ, angiotensin domain type 1 receptor-associated proteins.