title: Calcium-dependent cysteine reactivities in the neuronal calcium sensor guanylate cyclase-activating protein 1.
abstract: Guanylate cyclase-activating protein 1 (GCAP-1) is a Ca(2+)-sensing protein in vertebrate photoreceptor cells. It activates a membrane-bound guanylate cyclase. Three of four cysteines present in wild-type GCAP-1 were accessible to the thiol-modifying reagent 5,5'-dithio-bis-(2-nitrobenzoic acid) in the presence of Ca(2+). Only Cys106 became exposed to the solvent after Ca(2+)-chelation. Since Cys106 is located in EF-hand 3, we could determine an apparent K(D) of 2.9 microM for Ca(2+) binding to this site with a fast off-rate (t approximately 2 ms). We conclude that the rapid dissociation of Ca(2+) from EF-hand 3 in GCAP-1 triggers activation of guanylate cyclase in rod cells.
authors.affiliation: Institut für Biologische Informationsverarbeitung, Forschungzentrum Jülich, Germany.
authors.forename: J Y
authors.initials: JY
authors.lastname: Hwang
authors.forename: R
authors.initials: R
authors.lastname: Schlesinger
authors.forename: K W
authors.initials: KW
authors.lastname: Koch
mesh_terms: D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002417:Cattle; D003545:Cysteine / Q000378:metabolism*; D004220:Disulfides; D004228:Dithionitrobenzoic Acid / Q000494:pharmacology; D020832:EF Hand Motifs; D004533:Egtazic Acid / Q000494:pharmacology; D004789:Enzyme Activation; D006162:Guanylate Cyclase / Q000378:metabolism*; D051604:Guanylate Cyclase-Activating Proteins; D009154:Mutation; D009579:Nitrobenzoates / Q000378:metabolism; D012374:Rod Cell Outer Segment / Q000201:enzymology / Q000378:metabolism*; D013438:Sulfhydryl Compounds / Q000378:metabolism
chemical_list: D002135:Calcium-Binding Proteins; D004220:Disulfides; D051604:Guanylate Cyclase-Activating Proteins; D009579:Nitrobenzoates; D013438:Sulfhydryl Compounds; C011136:thionitrobenzoic acid; D004533:Egtazic Acid; D004228:Dithionitrobenzoic Acid; D006162:Guanylate Cyclase; D003545:Cysteine; D002118:Calcium