ISOLATION OF A PEPTIDE STRUCTURALLY RELATED TO MAMMALIAN CORTICOSTATINS FROM THE LAMPREY PETROMYZON-MARINUS

Peptides in an extract of skin from the agnathan Petromyzon marinus (s ea lamprey) were purified by reversed phase high-performance liquid ch romatography and characterized by Edman degradation. The primary struc ture of a cysteine- and arginine-rich peptide (termed lamprey corticos tatin-related peptide [LCRP]) was established as g-Cys-Cys-Val-Arg-Gly -Leu-Asn-Val-Tyr-Cys-Cys-Phe. Mass spectrometry indicated that all cys teine residues are intramolecularly linked. This amino acid sequence s hows structural similarity to rat corticostatin R4 and rabbit corticos tatin R1. In particular, LCRP contains the polyarginine sequence at th e N-terminus of the peptide that is believed to mediate both the inhib ition of ACTH-stimulated steroidogenesis and the antimicrobial (defens in-like) actions of the corticostatins.