Relaxin is an insulin-like peptide which is currently being developed as potential treatment for cardiovascular disease and has recently passed III clinical trials. Similar to insulin, relaxin cannot be administered orally. Thus, to design more effective drugs, a better understanding of molecular mechanism of relaxin is essential. The cognate receptor of relaxin is called Relaxin Family Peptide 1 (RXFP1). Structurally, RXFP1 consists of a 7-transmembrane domain and large ectodomain consisting of 10 leucine-rich repeats (LRR) domain and an N-terminal low density lipoprotein type A (LDLa) module. Relaxin is known to bind to the ectodomain of RXFP1 with high affinity; however, the exact mechanism of the interaction is currently unknown. Thus, the aim of this project is to investigate the binding mechanism of relaxin to RXFP1.
Previous studies suggest that relaxin have multiple binding sites within its receptor, more specifically the LRR domain, a region between LRR domain and LDLa module and the extracellular loops in the 7-transmembrane domain. Most of the studies utilised Nuclear Magnetic Resonance (NMR) and were done by using isotopically labelled domain of RXFP1. Since producing isotopically labelled synthetic relaxin is prohibitively expensive, the binding site of the receptor to relaxin remains unknown. Here, we describe an efficient method to produce isotopically labelled recombinant relaxin. The availability of isotopically labelled relaxin allows further NMR studies that is previously impossible which will give a valuable insight of how relaxin binds to its receptor. The results of this study will greatly contribute to the development of more efficient drug for cardiovascular disease.