Relaxin has conformational homology with insulin

Abstract

RELAXIN, a polypeptide hormone synthesised and stored in the corpus luteum, is responsible for the dilation of the symphysis pubis in most mammals before parturition. Porcine relaxin (molecular weight ∼5,600) consists of one A chain and one B chain linked by disulphide bonds. The amino acid sequence of the two chains is consistent with interchain and intrachain disulphide crosslinks of the same disposition as those of insulin^1,2. Although only five further residues are identical to those in equivalent positions of porcine insulin, the model presented here shows that relaxin may have a tertiary structure closely resembling that of insulin. The residues of the hydrophobic core of relaxin differ from those of insulin but are close packed and occupy the same volume.