A C-Type Natriuretic Peptide from The Venom of The Platypus (Ornithorhynchus anatinus) - Structure and Pharmacology.

Abstract

A peptide which relaxes rat uterine smooth muscle and exhibits homology with the mammalian C-type natriuretic peptide (CNP) has previously been identified in platypus venom. In this study we describe detailed structural and pharmacological characteristics of this peptide, which has been labelled ONP-39 (Ornithorhynchus Natriuretic Peptide). Elucidation of its 39-residue primary sequence confirms the substantial homology it shares with mammalian CNPs. These peptides exhibit natriuretic, diuretic and hypotensive activities in vivo and relax smooth muscle in vitro but are poorly characterised in terms of physiological function. ONP-39 is equipotent with CNP in causing cGMP elevation in cultured vascular smooth muscle cells, suggesting that, like CNP, it acts through ANPB receptors. The direct elevation of cGMP in vascular smooth muscle by ONP-39 may underlie vasodilatory effects of platypus venom.