Maruya M, Mitsui M, Murakami-Murofushi K
Department of Biology, Faculty of Science, Ochanomizu University, Tokyo, Japan.
Cell Struct Funct. 1996 Dec;21(6):533-8. doi: 10.1247/csf.21.533.
Protein kinase activities in myxoamoebae of a true slime mold, Physarum polycephalum, were investigated in response to heat shock. In-gel assay detected an apparent activation of a Ca(2+)-dependent, 53-kDa protein kinase that phosphorylated casein but not histone H1. This enzyme needed co-presence of Mg2+ ion with Ca2+ for activity. Treatment with calf intestinal alkaline phosphatase did not affect the heat-inducible 53-kDa protein kinase activity at all. The effects of protein kinase inhibitors were examined, and staurosporine suppressed the activity of this enzyme completely. H-7 decreased the activity to about 20% and HA-1004 to 65%. These results suggest that this protein kinase that may phosphorylate tyrosine and serine/threonine residues of target proteins is activated by heat shock in Physarum cells, and the activation is not regulated via phosphorylation by putative protein kinase(s) that may act at an upstream position in the signaling cascade(s).
为了研究热休克对多头绒泡菌（一种真正的黏菌）的变形体中蛋白激酶活性的影响，进行了相关实验。凝胶内分析检测到一种表观上被激活的、依赖Ca(2+)的53 kDa蛋白激酶，该激酶可磷酸化酪蛋白，但不能磷酸化组蛋白H1。这种酶需要Mg2+离子与Ca2+共同存在才能发挥活性。用小牛肠碱性磷酸酶处理对热诱导的53 kDa蛋白激酶活性完全没有影响。研究了蛋白激酶抑制剂的作用，星形孢菌素完全抑制了这种酶的活性。H-7将活性降低至约20%，HA-1004将活性降低至65%。这些结果表明，这种可能磷酸化靶蛋白酪氨酸和丝氨酸/苏氨酸残基的蛋白激酶在多头绒泡菌细胞中被热休克激活，并且该激活不是通过可能在信号级联上游起作用的假定蛋白激酶的磷酸化来调节的。
