title: Phosphorylation of an inhibitory subunit of cGMP phosphodiesterase in Rana catesbeiana rod photoreceptors. I. Characterization of the phosphorylation.
abstract: Interaction between the inhibitory subunit (P gamma) and catalytic subunits of cGMP phosphodiesterase is essential for the regulation of cGMP phosphodiesterase in vertebrate rod photoreceptors. P gamma phosphorylation in vitro has been studied using a kinase which is extracted from amphibian rod outer segments. Various chromatographies of the kinase preparation using ionic exchange, gel filtration, and heparin-Sepharose columns indicate that a kinase with M(r) 70,000 is responsible for the P gamma phosphorylation. The kinase does not require any of the known activators for protein kinases but is inhibited by cGMP in a concentration-dependent manner. Together with analysis by laser-desorption mass spectrometry, measurement of 32P radioactivity in phosphorylated P gamma indicates that P gamma extracted with GTP-bound transducin alpha subunit is not phosphorylated and that a phosphate is incorporated into more than 80% of the P gamma by the kinase. Phosphoamino acid analysis, sequencing of phosphorylated peptides derived from phosphorylated P gamma, and phosphorylation of synthetic peptides indicate threonine 22 in P gamma is phosphorylated by the kinase. Phosphorylated P gamma has a higher inhibitory activity for active cGMP phosphodiesterase than non-phosphorylated P gamma. These data suggest that threonine 22 in P gamma is phosphorylated by a specific kinase and that the P gamma phosphorylation governs the interaction between P gamma and catalytic subunits of cGMP phosphodiesterase in vertebrate rod photoreceptors.
authors.affiliation: Kresge Eye Institute, Department of Ophthalmology, Wayne State University, School of Medicine, Detroit, Michigan 48201.
authors.forename: S
authors.initials: S
authors.lastname: Tsuboi
authors.forename: H
authors.initials: H
authors.lastname: Matsumoto
authors.forename: K W
authors.initials: KW
authors.lastname: Jackson
authors.forename: K
authors.initials: K
authors.lastname: Tsujimoto
authors.forename: T
authors.initials: T
authors.lastname: Williams
authors.forename: A
authors.initials: A
authors.lastname: Yamazaki
mesh_terms: D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000818:Animals; D004789:Enzyme Activation; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000378:metabolism*; D006868:Hydrolysis; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D011892:Rana catesbeiana; D017948:Retinal Rod Photoreceptor Cells / Q000201:enzymology*; D013379:Substrate Specificity
chemical_list: D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate; D011494:Protein Kinases; D015106:3',5'-Cyclic-GMP Phosphodiesterases