Hayashi F, Lin G Y, Matsumoto H, Yamazaki A
Cellular and Molecular Biology Group, Los Alamos National Laboratory, University of California, NM 87545.
Proc Natl Acad Sci U S A. 1991 May 15;88(10):4333-7. doi: 10.1073/pnas.88.10.4333.
An inhibitory subunit (P gamma) of cGMP phosphodiesterase from vertebrate rod photoreceptors (frog, toad, and bovine) was phosphorylated by cytosolic protein kinase(s) derived from intact frog rod outer segments. The phosphorylation of frog P gamma was stimulated by phosphatidylinositol but not by cAMP or cGMP. One- and two-dimensional gel electrophoresis revealed that 70-80% of P gamma was phosphorylated with 1 mol of phosphate per frog P gamma under optimal conditions. A peptide that derived from an active domain of bovine P gamma was also phosphorylated. Phosphorylation of frog P gamma was inhibited by addition of the peptide to the reaction mixture. Phosphorylation of frog P gamma was also inhibited by addition of transducin subunits or active (P gamma-less) cGMP phosphodiesterase. Okadaic acid, on the other hand, enhanced P gamma phosphorylation, suggesting the presence of protein phosphatase(s) in the cytosolic fraction. These data suggest another mechanism for the regulation of cGMP phosphodiesterase in vertebrate rod photoreceptors.
来自脊椎动物视杆光感受器（青蛙、蟾蜍和牛）的cGMP磷酸二酯酶的抑制亚基（Pγ）被源自完整青蛙视杆外段的胞质蛋白激酶磷酸化。青蛙Pγ的磷酸化受磷脂酰肌醇刺激，但不受cAMP或cGMP刺激。一维和二维凝胶电泳显示，在最佳条件下，70 - 80%的Pγ被磷酸化，每分子青蛙Pγ结合1摩尔磷酸。源自牛Pγ活性结构域的一个肽段也被磷酸化。向反应混合物中添加该肽段可抑制青蛙Pγ的磷酸化。添加转导素亚基或活性（无Pγ）cGMP磷酸二酯酶也可抑制青蛙Pγ的磷酸化。另一方面，冈田酸增强了Pγ的磷酸化，表明胞质部分存在蛋白磷酸酶。这些数据提示了脊椎动物视杆光感受器中cGMP磷酸二酯酶调节的另一种机制。
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