Binding of GTP to transducin is not inhibited by arrestin and phosphorylated rhodopsin.
In the presence of a photobleaching intermediate of unphosphorylated or phosphorylated rhodopsin (Rh*), the binding of GppNHp to transducin was measured with or without arrestin for elucidation of the shut-off mechanism of the visual transduction process in bovine rod outer segments. The ability of Rh* to catalyze the formation of the transducin-GppNHp complex in the absence of arrestin was independent of the degree of phosphorylation of Rh*. Furthermore, the catalyzing ability of the phosphorylated Rh* was not reduced by the addition of arrestin. These observations indicate that the interaction between phosphorylated Rh* and transducin was not inhibited by arrestin. Thus, the hypothesis was not supported that the PDE shut-off process is a simple competition between transducin and arrestin for binding to phosphorylated Rh*.
Fukada
Y
Y
Department of Biophysics, Faculty of Science, Kyoto University, Japan.
Yoshizawa
T
T
Saito
T
T
Ohguro
H
H
Akino
T
T
D000818:Animals; D000941:Antigens / Q000494:pharmacology*; D019393:Arrestin; D002417:Cattle; D005136:Eye Proteins / Q000494:pharmacology*; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives*; D006165:Guanylyl Imidodiphosphate / Q000378:metabolism*; D008081:Liposomes / Q000378:metabolism; D010766:Phosphorylation; D012168:Retinal Pigments / Q000494:pharmacology*; D012243:Rhodopsin / Q000378:metabolism / Q000494:pharmacology*; D012374:Rod Cell Outer Segment / Q000032:analysis; D015293:Transducin / Q000378:metabolism*
D000941:Antigens; D019393:Arrestin; D005136:Eye Proteins; D008081:Liposomes; D012168:Retinal Pigments; D006165:Guanylyl Imidodiphosphate; D006160:Guanosine Triphosphate; D012243:Rhodopsin; D015293:Transducin