title: Inhibition of Rap1A binding to cytochrome b558 of NADPH oxidase by phosphorylation of Rap1A.
abstract: Rap1A is a low molecular weight guanosine triphosphate (GTP)-binding protein in human neutrophil membranes whose cellular function is unknown. Rap1A was found to form stoichiometric complexes with the cytochrome b558 component of the phagocyte nicotinamide adenine dinucleotide phosphate (NADPH) oxidase system. The (guanosine-5'-O-(3-thiotriphosphate) (GTP-gamma-S)-bound form of Rap1A bound more tightly to cytochrome b558 than did the guanosine diphosphate-bound form. No complex formation was observed between cytochrome b558 and H-Ras-GTP-gamma-S or Rap1A-GTP-gamma-S that had been heat-inactivated, nor between Rap1A-GTP-gamma-S and hydrophobic proteins serving as controls. Complex formation between Rap1A-GTP-gamma-S and cytochrome b558 was inhibited by phosphorylation of Rap1A with cyclic adenosine monophosphate (cAMP)-dependent protein kinase. These observations suggest that Rap1A may participate in the structure or regulation of the NADPH oxidase system and that this function of the Rap1A protein may be altered by phosphorylation.
authors.affiliation: Department of Immunology, Scripps Research Institute, La Jolla, CA 92037.
authors.forename: G M
authors.initials: GM
authors.lastname: Bokoch
authors.forename: L A
authors.initials: LA
authors.lastname: Quilliam
authors.forename: B P
authors.initials: BP
authors.lastname: Bohl
authors.forename: A J
authors.initials: AJ
authors.lastname: Jesaitis
authors.forename: M T
authors.initials: MT
authors.lastname: Quinn
mesh_terms: D001665:Binding Sites; D002850:Chromatography, Gel; D003573:Cytochrome b Group / Q000302:isolation & purification / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D046911:Macromolecular Substances; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism*; D019255:NADPH Oxidases; D009504:Neutrophils / Q000201:enzymology; D010766:Phosphorylation; D011485:Protein Binding; D011493:Protein Kinase C / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism; D020668:rap GTP-Binding Proteins
chemical_list: D003573:Cytochrome b Group; D046911:Macromolecular Substances; D011518:Proto-Oncogene Proteins; D011994:Recombinant Proteins; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C036888:cytochrome b558; D009247:NADH, NADPH Oxidoreductases; D019255:NADPH Oxidases; D011493:Protein Kinase C; D019204:GTP-Binding Proteins; D020668:rap GTP-Binding Proteins