Robinson L C, Menold M M, Garrett S, Culbertson M R
Laboratory of Molecular Biology, Robert M. Bock Laboratories, University of Wisconsin, Madison 53706.
Mol Cell Biol. 1993 May;13(5):2870-81. doi: 10.1128/mcb.13.5.2870-2881.1993.
Casein kinase I is an acidotropic protein kinase class that is widely distributed among eukaryotic cell types. In the yeast Saccharomyces cerevisiae, the casein kinase I isoform encoded by the gene pair YCK1 and YCK2 is a 60- to 62-kDa membrane-associated form. The Yck proteins perform functions essential for growth and division; either alone supports growth, but loss of function of both is lethal. We report here that casein kinase I-like activity is associated with a soluble Yck2-beta-galactosidase fusion protein in vitro and that thermolabile protein kinase activity is exhibited by a protein encoded by fusion of a temperature-sensitive yck2 allele with lacZ. Cells carrying the yck2-2ts allele arrest at restrictive temperature with multiple, elongated buds containing multiple nuclei. This phenotype suggests that the essential functions of the Yck proteins include roles in bud morphogenesis, possibly in control of cell growth polarity, and in cytokinesis or cell separation. Further, a genetic relationship between the yck2ts allele and deletion of CDC55 indicates that the function of Yck phosphorylation may be related to that of protein phosphatase 2A activity.
酪蛋白激酶I是一类嗜酸蛋白激酶，广泛分布于真核细胞类型中。在酿酒酵母中，由基因对YCK1和YCK2编码的酪蛋白激酶I同工型是一种60至62千道尔顿的膜相关形式。Yck蛋白执行生长和分裂所必需的功能；单独一个就能支持生长，但两者功能丧失则是致命的。我们在此报告，酪蛋白激酶I样活性在体外与可溶性Yck2-β-半乳糖苷酶融合蛋白相关，并且由温度敏感型yck2等位基因与lacZ融合编码的蛋白表现出热不稳定蛋白激酶活性。携带yck2-2ts等位基因的细胞在限制温度下停滞，带有多个含有多个细胞核的细长芽。这种表型表明，Yck蛋白的基本功能包括在芽形态发生中的作用，可能在细胞生长极性的控制中，以及在胞质分裂或细胞分离中。此外，yck2ts等位基因与CDC55缺失之间的遗传关系表明，Yck磷酸化的功能可能与蛋白磷酸酶2A活性的功能相关。
