Guilfoyle T J
Department of Biochemistry, University of Missouri, Columbia, 65211.
Plant Cell. 1989 Aug;1(8):827-36. doi: 10.1105/tpc.1.8.827.
A protein kinase from wheat germ that phosphorylates the largest subunit of RNA polymerase IIA has been partially purified and characterized. The kinase has a native molecular weight of about 200 kilodaltons. This kinase utilizes Mg2+ and ATP and transfers about 20 phosphates to the heptapeptide repeats Pro-Thr-Ser-Pro-Ser-Tyr-Ser in the carboxyl-terminal domain of the 220-kilodalton subunit of soybean RNA polymerase II. This phosphorylation results in a mobility shift of the 220-kilodalton subunits of a variety of eukaryotic RNA polymerases to polypeptides ranging in size from greater than 220 kilodaltons to 240 kilodaltons on sodium dodecyl sulfate-polyacrylamide gels. The phosphorylation is highly specific to the heptapeptide repeats since a degraded subunit polypeptide of 180 kilodaltons that lacks the heptapeptide repeats is poorly phosphorylated. Synthetic heptapeptide repeat multimers inhibit the phosphorylation of the 220-kilodalton subunit.
从小麦胚芽中分离得到一种能使RNA聚合酶IIA最大亚基磷酸化的蛋白激酶,并对其进行了部分纯化和特性鉴定。该激酶的天然分子量约为200千道尔顿。此激酶利用Mg2+和ATP,并将约20个磷酸基团转移至大豆RNA聚合酶II 220千道尔顿亚基羧基末端结构域中的七肽重复序列Pro-Thr-Ser-Pro-Ser-Tyr-Ser上。这种磷酸化作用导致多种真核生物RNA聚合酶的220千道尔顿亚基在十二烷基硫酸钠-聚丙烯酰胺凝胶上的迁移率发生变化,变为大小从大于220千道尔顿到240千道尔顿不等的多肽。由于缺乏七肽重复序列的180千道尔顿降解亚基多肽磷酸化程度较低,所以这种磷酸化作用对七肽重复序列具有高度特异性。合成的七肽重复多聚体可抑制220千道尔顿亚基的磷酸化。