Myosin Light Chaiu Kinase in sea urchin egg

我们分析了海胆未受精和受精卵提取液中肌球蛋白轻链激酶(MLCK)的活性。体外实验中，使Mysion-II调节轻链(MLC)磷酸化的总激酶活性在未受精卵提取液中高于受精卵提取液。磷酸肽图分析表明，未受精卵中的激酶活性分别在从鸡胆中纯化的MLCK(CgMLCK)和蛋白激酶C(PKC)磷酸化的位置对MLC进行磷酸化。在中期，使MLC在cgMLCK位点磷酸化的激酶活性降低，而使MLC在PKC位点磷酸化的激酶活性升高。用凝胶过滤层析对未受精卵提取物进行分级，得到海胆MLCK活性的两个峰(称为组分I和组分II)。前肽图谱分析表明，这两种酶都能磷酸化cgMLCK位点上的MLC，但一个是钙调素依赖性的MLCK，另一个是钙调素非依赖性的MLCK。

We have analyzed myosin light chain kinase (MLCK) activities in unfertilized and fertilized egg extracts from sea urchin, Hemicentrotus pulcherrimus. Total kinase activities that phosphorylates regulatory light chain of mysion-II (MLC) are higher in unfertilized egg extracts than in fertilized egg extracts in vitro. Phosphopeptide mapping analysis shows that the kinase activities in unfertilized eggs phosphorylate MLC both at the sites which MLCK purified from chicken gizzard (cgMLCK) and protein kinase C (PKC) phosphorylate, respectively. In metaphase, the kinase activity that phosphorylates MLC at cgMLCK sites is decreased, but the kinase activity that phosphorylates MLC at PKC sites is increased. Fractionation of undfertilized egg extracts using a gel filtration chromatography resulted in two peaks (termed fraction I and fraction II) of sea urchin MLCK activities. Prosphopeptide mapping analsis shows that both kinases phosphorylate MLC at cgMLCK sites but one is calciumcalmodulin dependent MLCK and the other is calciumcalmodulin independent MLCK,respectively.