title: A site on transducin alpha-subunit of interaction with the polycationic region of cGMP phosphodiesterase inhibitory subunit.
abstract: Activation of cGMP phosphodiesterase (PDE) by the rod G-protein transducin is a key event in visual signal transduction in vertebrate photoreceptor cells. Interaction between the GTP-bound form of the alpha-subunit of transducin (alpha t*) and the PDE inhibitory gamma-subunit (P gamma) is a major component of PDE activation. The central polycationic region of P gamma, P gamma-24-45, has been implicated as one of the sites involved in alpha t*.P gamma interaction. Here we determine the site on alpha t* that interacts with P gamma-24-45 using a photo-cross-linking approach. The synthetic peptides Cys(ACM)Tyr-P gamma-24-45-Cys (where ACM indicates acetamidomethyl group) and Cys-P gamma-24-45 were labeled with 4-(N-maleimido)benzophenone at the COOH and NH2 termini, respectively, and then cross-linked to alpha t. When the photoprobe was attached to the COOH terminus of the peptide, a specific high yield cross-linked product (80%) was formed between the peptide and alpha t GTP gamma S (guanosine 5'-O-(thiotriphosphate)). A lower yield of cross-linking (35%) was seen between the peptide and alpha t GDP. The site of cross-linking between Cys(ACM)Tyr-P gamma-24-45-Cys and alpha t GTP gamma S was localized to within alpha t-306-310 using a variety of chemical and proteolytic cleavages of the cross-linked product, analysis of the fragments with SDS-polyacrylamide gel electrophoresis, and matrix-assisted laser desorption ionization mass spectrometry.
authors.affiliation: Department of Physiology and Biophysics, University of Illinois College of Medicine, Chicago 60680.
authors.forename: N O
authors.initials: NO
authors.lastname: Artemyev
authors.forename: J S
authors.initials: JS
authors.lastname: Mills
authors.forename: K R
authors.initials: KR
authors.lastname: Thornburg
authors.forename: D R
authors.initials: DR
authors.lastname: Knapp
authors.forename: K L
authors.initials: KL
authors.lastname: Schey
authors.forename: H E
authors.initials: HE
authors.lastname: Hamm
mesh_terms: D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000737:chemistry / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002417:Cattle; D003432:Cross-Linking Reagents; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D046911:Macromolecular Substances; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry; D012374:Rod Cell Outer Segment / Q000737:chemistry; D015293:Transducin / Q000737:chemistry / Q000378:metabolism*
chemical_list: D003432:Cross-Linking Reagents; D046911:Macromolecular Substances; D010455:Peptides; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D015106:3',5'-Cyclic-GMP Phosphodiesterases; D015293:Transducin