NMR Studies of Zinc-binding Luteinizing Hormone Releasing Hormone

Abstract

Luteinizing Hormone Releasing Hormone(LHRH) is a decapeptide neurotransmitter known to be regulated by metal ions in the hyperthalamus. Zn-binding LHRH complex was systhesized, and zinc-LHRH complex was studied to understand what kinds of structural modifications would be critical in the LHRH releasing mechanism. Both nonexchangeable and exchangeable 1H−NMR signal assignments were accomplished by pH-dependent and COSY NMR experiments. In addition, 1H−NMR chemical shift changes of a-proton and peptide NH NMR signals at different pH condition, and 1H−NMR signal differences between metal free and metallo-LHRH complex was monitored. NMR signals exhibit that primary metal-binding sites are nitrogens donor of imidazole ring and Arg, and peptide oxygen of Pro-His in the sequence. Structure obtained in this study has a cyclic conformation which is similar to that of energy minimized, and exhibits a specific a-helical turn with residue numbers (2∼7) out of 10 amino acids.