Partial characterization of a putative allatostatin receptor in the midgutof the cockroach Diploptera punctata

Dippu-allatostatins (Dippu-ASTs) are a family of peptides originally isolat ed from the cockroach Diploptera punctata which appear to be pleiotropic in function. All members of the family are able to inhibit the biosynthesis o f juvenile hormone by corpora allata in vitro. In addition, ASTs are able t o modulate the contraction of visceral muscles and may play a role in the r egulation of digestive enzyme secretion by the midgut. We have identified a putative AST receptor in the cockroach midgut using a radioligand-binding assay. I-125-Dippu-AST 7 binding to midgut membranes was specific, saturabl e, and reversible. The midgut appears to contain a single class of binding sites for Dippu-AST 7, with K-d of 20.9 +/- 3.6 nM and B-max of 1.8 +/- 0.1 5 pmol . mg(-1) membrane protein. The relative affinity of the 13 members o f the Dippu-AST family was determined using a single-point competitive bind ing assay. Dippu-AST 7 and 2 appear to have higher affinity for the midgut AST receptor than Dippu-AST 5, 9, 10, or 11. Other Dippu-ASTs were unable t o compete with I-125-Dippu-AST 7 for binding, even at high concentration. ( C) 2000 Academic Press.