The RRASK motif in Xenopus cyclin B2 is required for the substrate recognition of Cdc25C by the cyclin B-Cdc2 complex
The RRASK motif in Xenopus cyclin B2 is required for the substrate recognition of Cdc25C by the cyclin B-Cdc2 complex
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DOI：
10.1074/jbc.m300210200
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发表时间：
2003-05-23
影响因子：
4.8
通讯作者：
Kobayashi, H
中科院分区：
文献类型：
--
作者：
Goda, T;Ishii, T;Kobayashi, H
FLRRXSK序列在B型细胞周期蛋白的第二个细胞周期蛋白盒折叠中是保守的。我们表明，这种保守的序列在非洲爪蟾细胞周期蛋白B2，称为RRASK基序，所需的基板识别的细胞周期蛋白B-Cdc 2复合物的Cdc 25 C。细胞周期蛋白B2的RRASK基序的带电残基的突变废除了其激活Cdc 2激酶的能力，而不影响其与Cdc 2结合的能力。Cdc 25 C不能使与细胞周期蛋白B2 RRASK突变体结合的Cdc 2去磷酸化，因此，复合物是无活性的。细胞周期蛋白B2 RRASK突变体可以与组成型活性Cdc 2形成复合物，但所得的活性复合物在体外没有磷酸化优选的底物Cdc 25 C，尽管它可以磷酸化非特异性底物组蛋白H1。RRASK突变阻止Cdc 25 C与细胞周期蛋白B2-Cdc 2复合物的相互作用。一致的是，RRASK突变体既不诱导非洲爪蟾卵母细胞成熟中的生殖囊泡破裂，也不激活体内Cdc 2激酶在有丝分裂提取物的细胞周期期间。这些结果表明，在爪蟾细胞周期蛋白B2的RRASK基序起着重要的作用，在定义的底物特异性的细胞周期蛋白B-Cdc 2复合物。
The FLRRXSK sequence is conserved in the second cyclin box fold of B-type cyclins. We show that this conserved sequence in Xenopus cyclin B2, termed the RRASK motif, is required for the substrate recognition by the cyclin B-Cdc2 complex of Cdc25C. Mutations to charged residues of the RRASK motif of cyclin B2 abolished its ability to activate Cdc2 kinase without affecting its capacity to bind to Cdc2. Cdc2 bound to the cyclin B2 RRASK mutant was not dephosphorylated by Cdc25C, and as a result, the complex was inactive. The cyclin B2 RRASK mutants can form a complex with the constitutively active Cdc2, but a resulting active complex did not phosphorylate a preferred substrate Cdc25C in vitro, although it can phosphorylate the nonspecific substrate histone H1. The RRASK mutations prevented the interaction of Cdc25C with the cyclin B2-Cdc2 complex. Consistently, the RRASK mutants neither induced germinal vesicle breakdown in Xenopus oocyte maturation nor activated in vivo Cdc2 kinase during the cell cycle in mitotic extracts. These results suggest that the RRASK motif in Xenopus cyclin B2 plays an important role in defining the substrate specificity of the cyclin B-Cdc2 complex.