title: Interspecies conservation of retinal guanosine 5'-triphosphatase. Characterization by photoaffinity labelling and tryptic-peptide mapping.
abstract: Light-activated hydrolysis of cyclic GMP is achieved through the photoexcitation of rhodopsin, a process which then triggers the replacement of GDP for GTP by a retinal guanosine 5'-triphosphatase referred to as 'transducin'. The transducin-GTP complex then switches on the phosphodiesterase [Fung, Hurley & Stryer (1981) Proc. Natl. Acad. Sci. U.S.A. 78, 152-156]. The bovine transducin consists of an alpha-subunit (39000 Mr), which is a GTP-binding component, together with a beta-(37000 Mr) and a gamma-subunit (10000 Mr). We have purified retinal transducin from cow, pig, chick and frog. The enzyme specific activities and sodium dodecyl sulphate/polyacrylamide-gel-electrophoretic profiles indicate that this enzyme is similar in all species except the frog. Whereas the bovine, pig and chick transducins consist of major 37000- and 39000-Mr components, that of the frog consists of a single 75000-Mr component. Labelling of the GTP-binding components with the photoaffinity label 8-azidoguanosine [gamma-32P]triphosphate demonstrated that the 37000-Mr components of the cow, pig and chick and the 75000-Mr component of the frog were major GTP-binding components. In addition, peptide maps of radioiodinated tryptic peptides indicate that the frog 75000-Mr protein is highly related to the pig transducin. These results demonstrate evolutionary conservation of retinal transducin and the presence of a higher-Mr, but nonetheless highly conserved form, of transducin in the frog. The relationship of this component to the recently reported rod-outer-segment inhibitor protein [Yamazaki, Stein, Chernoff & Bitensky (1983) J. Biol. Chem. 258, 8188-8194] is discussed.
authors.forename: M M
authors.initials: MM
authors.lastname: McMurray
authors.forename: J S
authors.initials: JS
authors.lastname: Hansen
authors.forename: B E
authors.initials: BE
authors.lastname: Haley
authors.forename: D J
authors.initials: DJ
authors.lastname: Takemoto
authors.forename: L J
authors.initials: LJ
authors.lastname: Takemoto
mesh_terms: D000818:Animals; D002417:Cattle; D002645:Chickens; D002846:Chromatography, Affinity; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D010446:Peptide Fragments / Q000032:analysis; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D011894:Rana pipiens; D012160:Retina / Q000201:enzymology*; D012374:Rod Cell Outer Segment / Q000378:metabolism; D013045:Species Specificity; D013552:Swine; D015293:Transducin; D014357:Trypsin
chemical_list: D008565:Membrane Proteins; D010446:Peptide Fragments; D010744:Phosphoric Monoester Hydrolases; D014357:Trypsin; D020558:GTP Phosphohydrolases; D015293:Transducin