McMichael R W, Lagarias J C
Department of Biochemistry and Biophysics, University of California, Davis 95616.
Biochemistry. 1990 Apr 24;29(16):3872-8. doi: 10.1021/bi00468a011.
We previously demonstrated that protein kinases are useful probes of conformational changes that occur upon photoconversion of phytochrome [Wong, Y.-S., Cheng, H.-C., Walsh, D. A., & Lagarias, J. C. (1986) J. Biol. Chem. 261, 12089-12097]. Here we present phosphopeptide analyses of oat phytochrome phosphorylated by three mammalian protein kinases and by a polycation-stimulated, phytochrome-associated protein kinase. Phosphorylation of the Pr form by the cAMP-dependent protein kinase occurs predominantly on Ser17 while Ser598 is the preferred phosphorylation site on Pfr. The cGMP-dependent and Ca2(+)-activated, phospholipid-dependent protein kinases, which phosphorylate only the Pr form of phytochrome, recognize the same region on the phytochrome polypeptide as the cAMP-dependent protein kinase. Polycation-stimulated phytochrome phosphorylation reveals that, in contrast to the mammalian enzymes, the plant kinase recognizes the serine-rich, blocked N-terminus of phytochrome. The potential regulatory role of phytochrome phosphorylation, particularly in the structurally conserved serine/threonine-rich N-terminal region of the phytochrome polypeptide, is suggested by these results.
我们先前已证明，蛋白激酶是研究光敏色素光转化时发生的构象变化的有用探针[Wong, Y.-S., Cheng, H.-C., Walsh, D. A., & Lagarias, J. C. (1986) J. Biol. Chem. 261, 12089 - 12097]。在此，我们展示了燕麦光敏色素被三种哺乳动物蛋白激酶以及一种多阳离子刺激的、与光敏色素相关的蛋白激酶磷酸化后的磷酸肽分析结果。cAMP依赖性蛋白激酶对Pr形式的磷酸化主要发生在Ser17，而Ser598是Pfr的优先磷酸化位点。cGMP依赖性和Ca2(+)激活的、磷脂依赖性蛋白激酶仅对光敏色素的Pr形式进行磷酸化，它们在光敏色素多肽上识别的区域与cAMP依赖性蛋白激酶相同。多阳离子刺激的光敏色素磷酸化表明，与哺乳动物酶不同，植物激酶识别光敏色素富含丝氨酸的、封闭的N端。这些结果提示了光敏色素磷酸化的潜在调节作用，特别是在光敏色素多肽结构保守的富含丝氨酸/苏氨酸的N端区域。
