title: Identification and partial characterization of the receptor for speract.
abstract: Here, we report the first identification of a sperm receptor for an egg-associated peptide (speract). Gly-Gly-Gly-Gly-Tyr-Asp-Leu-Asn-Gly-Gly-Gly-Val-Gly (GGG[Y2]-speract), was chemically synthesized and shown to possess equivalent respiration-stimulating activity and the same receptor binding characteristics as speract (Gly-Phe-Asp-Leu-Asn-Gly-Gly-Gly-Val-Gly). The incubation of Strongylocentrotus purpuratus intact sperm cells with radioiodinated GGG[Y2]-speract and the chemical cross-linking reagent, disuccinimidyl suberate, resulted in the appearance of a single radiolabeled band with an estimated Mr = 77,000 (determined by Na dodecyl SO4-gel electrophoresis under reducing conditions). The covalent coupling of 125I-GGG[Y2]-speract was prevented by biologically active analogues of speract but not by inactive analogues and the 125I analogue was not detectably coupled to any protein in Arbacia punctulata spermatozoa, a species with which speract does not cross-react. Comparisons of the amount of 125I-GGG[Y2]-speract bound in the presence of variable concentrations of unlabeled GGG[Y2]-speract showed that about 1 nM unlabeled peptide reduced 125I-GGG[Y2]-speract binding by 50% when estimated as either specific binding to intact cells or as the reduction in radioactivity found in the 77,000 molecular-weight band on autoradiographs after covalent coupling. The radiolabeled receptor could be solubilized with 0.5% Lubrol PX and was bound to wheat germ lectin-Sepharose. It could be subsequently eluted with N-acetylglucosamine or diacetylchitotriose but not by methyl-alpha-D-mannoside or NaCl, suggestive that the receptor is a glycoprotein.
mesh_terms: D000818:Animals; D004591:Electrophoresis, Polyacrylamide Gel; D036341:Intercellular Signaling Peptides and Proteins; D008297:Male; D008970:Molecular Weight; D009842:Oligopeptides / Q000378:metabolism*; D010101:Oxygen Consumption; D010455:Peptides / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism*; D012617:Sea Urchins; D013094:Spermatozoa / Q000378:metabolism*; D013388:Succinimides / Q000378:metabolism
chemical_list: D036341:Intercellular Signaling Peptides and Proteins; D009842:Oligopeptides; D010455:Peptides; D011956:Receptors, Cell Surface; D013388:Succinimides; C035027:egg surface sperm receptor; C043494:glycyl-glycyl-glycyl-glycyl-tyrosyl-aspartyl-leucyl-asparaginyl-glycyl-glycyl-glycyl-valyl-glycine; C028364:speract; C019358:disuccinimidyl suberate