Phosphatidylinositol stimulates phosphorylation of protein components I and II in rod outer segments of frog photoreceptors.
We studied the effect of phosphoinositides on the phosphorylation of endogenous proteins in the soluble fraction of the frog photoreceptor rod outer segments (ROS). Phosphatidylinositol (PI) stimulated the phosphorylation of two low molecular weight proteins, components I and II (12 and 11 kDa) which are known to be the preferential substrates of the cyclic GMP (cGMP)-dependent protein kinase in the ROS. Polyphosphoinositides (PPI) specifically inhibited the PI-dependent phosphorylation of these two components. On the other hand, PPI stimulated the phosphorylation of 38, 48 and 52 kDa proteins in the absence of PI. These data suggest that PI and PPI may function in the ROS by regulating the phosphorylation of some enzymes or regulator proteins in the transduction mechanism in the ROS.
Hayashi
F
F
Department of Biology, College of General Education, Kobe University, Japan.
Sumi
M
M
Amakawa
T
T
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D006152:Cyclic GMP / Q000494:pharmacology; D007700:Kinetics; D018129:Phosphatidylinositol Phosphates; D010716:Phosphatidylinositols / Q000494:pharmacology*; D010761:Phosphorus Radioisotopes; D010766:Phosphorylation; D010786:Photoreceptor Cells / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*; D011892:Rana catesbeiana; D012374:Rod Cell Outer Segment / Q000378:metabolism*
D018129:Phosphatidylinositol Phosphates; D010716:Phosphatidylinositols; D010761:Phosphorus Radioisotopes; D011506:Proteins; D000255:Adenosine Triphosphate; D011494:Protein Kinases; D006152:Cyclic GMP