Bovine pineal antireproductive tripeptide binds to luteinizing hormone-releasing hormone: a model for peptide modulation by sequence specific peptide interactions?

We report results of chromatographic, pH titration and nuclear magnetic resonance (NMR) spectroscopy studies demonstrating that the bovine pineal antireproductive tripeptide, Thr-Ser-Lys (BPART), binds to luteinizing hormone-releasing hormone (LHRH) at a site comprised of LHRH 2-5 (His-Trp-Ser-Tyr). BPART and LHRH have been shown to be antagonists in vitro. The binding constant is ca. 2 X 10(3)/mole. An NMR study of fifty other peptide pairs demonstrates that the binding is sequence and residue specific. The binding provides evidence of the amino acid pairing hypothesis, and suggests the possibility of modulation of one peptide by directly binding with another peptide.