| Type: | Family | Name: | Relaxin |
| Description: | The insulin family of proteins groups together several evolutionarily related active peptides []: these include insulin [, ], relaxin [, ], insect prothoracicotropic hormone (bombyxin) [], insulin-like growth factors (IGF1 and IGF2) [, ], 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 [, , ]. 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 []. 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 []. Synthesised in the corpora lutea of ovaries during pregnancy, relaxin is released into the blood stream prior to parturition []. 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 []. | Short Name: | Relaxin |
