酵母细胞分裂周期突变株中磷酸化蛋白的变化

最近对酵母细胞腺苷酸环化酶和依赖于cAMP的蛋白激酶基因的分子生物学研究,说明磷酸化蛋白在细胞周期中有重要作用。本文用聚丙烯酰胺凝胶电泳研究了酵母细胞分裂周期突变株中蛋白质的磷酸化。依赖cAMP的突变株AM18生长在无cAMP的培基中时,发生了几种磷酸化蛋白的变化,最明显的是分子量为72K Da的蛋白的积聚。细胞分裂周期温度敏感突变株cdc35生长在高于允许温度对,以及野生株生长在稳定期时,也出现类似现象。在这三种情况下,72K Da磷酸化蛋白同时还具有相同的pI值(pI=4.7),磷酸化都发生在苏氨酸残基上,用蛋白酶部分水解法证明它们有相似的肽谱。这些结果说明它们为同一蛋白。

Phosphoprotein Changes in Yeast Cell-Division-Cycle Mutants

Recent molecular biological studies on adenylate cyclase and cAMP-dependent protein kinase gene of yeast have indicated the importance of protein phosphoryla-tion in the control of cell cycle. In vivo protein phosphorylation in yeast was studied by one and two dimensional polyacrylamide gel electrophoresis in cell-division-cycle mutants.At cAMP-free medium,cAMP-dependent yeast mutant AM18 showed several phosphoprotein cnanges. The most prominent change is an accumulation of a 72k Da protein (PP72).PP72 was also highly phosphorylated in cdc 35, a "start" mutant, at non-permissive temperature, and in wild type cells, A363A (22244) , at stationary phase. In all three cases, PP72 was phosphorylated at threonine, and had the same PI value (pH4.7) , and showed the similar peptide map by partial protease hydrolysis, suggestting that they are same protein.