Introduction of relaxin properties into other hormones of insulin-like structure.

Sequence comparison of natural relaxins and the investigation of the structure function relationship of chemically synthesized relaxin analogs have been used to identify two arginine residues on the surface of the main helix of the B chain as hormone-receptor interaction site. This site is sensitive to structural changes, in particular the conformation of the A chain loop. Introducing the active site of relaxin into noncrossreacting structural analogs such as insulin and bombyxin required a four amino acid exchange. Both hybrid hormones bound to the anti-porcine relaxin antibody R6 with high affinity, and the insulin analog, with an additional C-terminal truncation of the B chain, crossreacted with rat relaxin-receptors.