AJP - Endocrinology and Metabolism, Vol 261, Issue 3 E319-E324, Copyright © 1991 by American Physiological Society
Structural requirements of pancreatic polypeptide receptor binding
R. L. Gingerich, J. O. Akpan, W. R. Gilbert, K. M. Leith, J. A. Hoffmann and R. E. Chance
Department of Pediatrics, Washington University, St. Louis, Missouri 63110.
Pancreatic polypeptide (PP) receptors have been identified and
characterized on the basolateral membranes (BLM) of canine intestinal
mucosa. The present study was designed to ascertain the structural
requirements of the PP molecule for binding to its receptor. A
radioreceptor assay using purified BLM was employed to elucidate receptors
specific to PPs of various mammalian species and to modified bovine PP
(bPP) fragments. Receptor cross-reactivities (CR) to various PPs and bPP
fragments were established. Results show that percent receptor CR by PPs of
various species was as follows: bPP (100%) greater than human PP (68%)
greater than porcine PP (50%) greater than canine PP (45%) greater than
ovine PP (36%) greater than rat PP (3%). The fragments bPP-(1-15),
bPP-(1-17), bPP-(1-26), bPP-(16-23), bPP-(18-30), bPP-(24-36), bPP-(27-35),
and bPP-(31-36) at 500 nM did not significantly displace tracer from
receptor (less than 0.1% CR). Des-COOH-terminal tyrosinamide [bPP-(1-35)]
produced less than 0.1% CR. Oxidation of bPP methionine-30 residue to
methionine sulfoxide decreased displacement to 67%. Modification of native
amidated tyrosinamide to the free acid abolished receptor binding, whereas
esterification to the methyl ester of COOH-terminal tyrosine restored
binding to 60%. Additionally, percent CR decreased progressively as amino
acid residues were deleted from the NH2-terminal region. We conclude that
the molecular homologue of PP primary structure is necessary for full
receptor binding. Both the NH2- and COOH-terminal residues are required for
recognition, and the COOH-terminal tyrosinamide must be intact for PP
binding to its receptor.
