Characterization of a diuretic hormone receptor from the tobacco hornworm, Manduca sexta

Abstract

AbstractWe have characterized a diuretic hormone receptor from the tobacco hornworm, Manduca sexta. A single high affinity binding site for the 41 amino acid M. sexta diuretic hormone was found in membranes prepared from Malpighian tubules of fifth stadium larvae. The site has a Kd = 79 pM and Bmax = 3.1 pmol/mg protein. The dissociation rate constant was determined to be 0.11 min−1 with a corresponding half‐life of 6.4 min. Receptor binding of the hormone is inhibited by Ca2+ and Mg2+, while Na+ and K+ inhibit binding to a lesser extent. Truncated diuretic hormone analogs in which up to 20 amino acids were removed from the N‐terminus maintain high affinity for the receptor. A diuretic hormone from Locusta migratoria which has 43% sequence identity with the M. sexta diuretic hormone also possesses a high affinity for the receptor. Conformational analysis of the M. sexta diuretic hormone indicates the core region of the peptide assumes a helical conformation, which may have implications in the binding of the peptide to the receptor. © 1993 Wiley‐Liss. Inc.