GTP binding protein: Properties and lack of activation by phosphorylated rhodopsin

• Published in: Vision Research [VISION RES.]. Vol. 24, no. 11. 1984 Vol. 24; no. 11; pp. 1523 - 1531
• Main Authors: Shichi, Hitoshi, Yamamoto, Katsuhiko, Somers, Robert L.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: England Elsevier Ltd 1984
• Subjects: Animals; Cattle; Circular Dichroism; Electrophoresis, Polyacrylamide Gel; Eye Proteins - metabolism; GTP-Binding Proteins - metabolism; Guanine Nucleotides - metabolism; Guanosine Triphosphate - metabolism; Heterotrimeric GTP-Binding Proteins; Membrane Proteins - metabolism; Phosphorylation; Retinal Pigments - pharmacology; rhodopsin; Rhodopsin - pharmacology
• ISSN: 0042-6989; 1878-5646
• DOI: 10.1016/S0042-6989(84)80001-2

Taking advantage of the capability of GTP binding protein to bind GTP, we purified thecatalytic subunit (Gg) of bovine rod GTP binding protein by nucleotide-affinity chromatography on Blue Sepharose CL6B. Purified Gα was essentially free of bound guanine nucleotide and activated by photoactivated rod membranes. Circular dichroism spectra suggested that a significant portion of the protein would be in α-helical conformation. No appreciable differences were detected in the circular dichroism spectra when Gα. GDP and Gα. GppNp were compared. The extent of G protein activation by rod membranes was reduced moderately by phosphorylation of rhodopsin during photolysis. However, if the pigment had been phosphorylated and regenerated, the ability of rhodopsin to activate G protein was markedly suppressed.