Relaxin (IPR022421)

Short name: Relaxin

Overlapping homologous superfamilies

Family relationships


The insulin family of proteins groups together several evolutionarily related active peptides [PMID: 6107857]: these include insulin [PMID: 6243748, PMID: 503234], relaxin [PMID: 10601981, PMID: 8735594], insect prothoracicotropic hormone (bombyxin) [PMID: 8683595], insulin-like growth factors (IGF1 and IGF2) [PMID: 2036417, PMID: 1319992], mammalian Leydig cell-specific insulin-like peptide (gene INSL3), early placenta insulin-like peptide (ELIP) (gene INSL4), locust insulin-related peptide (LIRP), molluscan insulin-related peptides (MIP), and Caenorhabditis elegans insulin-like peptides. The 3D structures of a number of family members have been determined [PMID: 2036417, PMID: 1319992, PMID: 9141131]. The fold comprises two polypeptide chains (A and B) linked by two disulphide bonds: all share a conserved arrangement of 4 cysteines in their A chain, the first of which is linked by a disulphide bond to the third, while the second and fourth are linked by interchain disulphide bonds to cysteines in the B chain.

Relaxin is encoded by two non-allelic genes in humans and great apes, and by a single gene in all other species studied to date [PMID: 8735594]. The expression of human relaxin genes (H1 and H2) has been characterised in placenta, decidua, prostate and ovary: H2 relaxin mRNA was detected in the ovary, term placenta, decidua, and prostate gland; by contrast, H1 gene expression was detected only in the prostate gland [PMID: 8735594]. Synthesised in the corpora lutea of ovaries during pregnancy, relaxin is released into the blood stream prior to parturition [PMID: 6298628]. With oestrogen, it acts to produce dilation of the birth canal in many mammals, its major biological role being to remodel the reproductive tract to facilitate the birth process [PMID: 6298628].

GO terms

Biological Process

No terms assigned in this category.

Molecular Function

GO:0005179 hormone activity

Cellular Component

GO:0005576 extracellular region

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.