Department of Biochemistry, University of Nebraska-Lincoln, Lincoln, Nebraska 68583-0718.
Plant Physiol. 1989 Jan;89(1):238-43. doi: 10.1104/pp.89.1.238.
Chloroplast thylakoid protein phosphatase activity was measured using (32)P-labeled histone as an exogenous substrate and an assay of the (32)Pi released involving formation of a phosphomolybdate complex and organic extraction. The activity was liberated from wheat (Triticum aestivum) thylakoids by washing the membranes in NaCl-containing solutions followed by centrifugation. The liberated phosphatase activity had a pH optimum of approximately 6.75, was inhibited by addition of 10 millimolar EDTA or EGTA, and was stimulated by addition of millimolar amounts of dithiothreitol, magnesium, manganese, or calcium ions. The rate of thylakoid protein dephosphorylation was decreased following liberation of a portion of the protein phosphatase activity and was increased by addition of salt-liberated phosphatase fraction. These results suggest that at least a portion of wheat thylakoid protein phosphatase is a peripheral, rather than an integral, membrane protein.
叶绿体类囊体蛋白磷酸酶活性是使用(32)P 标记的组蛋白作为外源底物,并通过(32)Pi 的释放来测量的,涉及到形成磷钼酸盐复合物和有机提取。该活性是通过在含有 NaCl 的溶液中洗涤膜并离心从小麦(Triticum aestivum)类囊体中释放出来的。释放的磷酸酶活性的 pH 最佳值约为 6.75,可被添加 10 毫摩尔 EDTA 或 EGTA 抑制,并可被添加毫摩尔量的二硫苏糖醇、镁、锰或钙离子刺激。在释放部分蛋白磷酸酶活性后,类囊体蛋白去磷酸化的速率降低,并可通过添加盐释放的磷酸酶部分来增加。这些结果表明,至少一部分小麦类囊体蛋白磷酸酶是一种外周蛋白,而不是膜整合蛋白。