ROLE OF COOH-TERMINAL PHOSPHORYLATION IN THE REGULATION OF CASEIN KINASE I-DELTA
ROLE OF COOH-TERMINAL PHOSPHORYLATION IN THE REGULATION OF CASEIN KINASE I-DELTA
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DOI：
10.1074/jbc.270.37.21689
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发表时间：
1995-09-15
影响因子：
4.8
通讯作者：
ROACH, PJ
中科院分区：
文献类型：
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作者：
GRAVES, PR;ROACH, PJ
酪蛋白激酶I δ是酪蛋白激酶I （CKI）家族的一员，是一组第二信使非依赖性蛋白激酶。我们提出证据表明CKI δ的cooh末端结构域具有调控特性。如前所述，大肠杆菌中表达的CKI δ可被肝素激活，并可通过1型蛋白磷酸酶（CS1）的催化亚基处理。在十二烷基硫酸钠存在的情况下，通过聚丙烯酰胺凝胶电泳判断，随着CS1的激活，CKI δ的表观分子量从55,000减少到49,000。通过去除cooh末端110个氨基酸来截断CKI δ，消除了CS1激活或增加电泳迁移率的能力。酪蛋白激酶I α是一种37-kDa的异构体，缺乏延伸的cooh末端结构域，不被CS1或肝素激活。然而，由CKI α组成的嵌合酶融合到CKI δ的cooh末端结构域，可被肝素和CS1激活。通过分析CS1对一系列CKI δ cooh末端截断突变体的影响，在His（317）和Pro（342）之间发现了一个抑制区域，该区域包含6个潜在的磷酸化位点。从这些截断突变体的特异活性分析来看，去除相同区域导致酶的特异活性比野生型高近10倍。因此，CKI δ活性可以通过其COOH末端的磷酸化来调节，这可能有助于创建一个自抑制结构域。这种调节机制可能在体内产生重要影响。
Casein kinase I delta is a member of the casein kinase I (CKI) family, a group of second messenger independent protein kinases. We present evidence that the COOH-terminal domain of CKI delta has regulatory properties. CKI delta expressed in Escherichia coli was activated by heparin, as found previously, and by treatment with the catalytic subunit of type-1 protein phosphatase (CS1). Concomitant with activation by CS1, there was a reduction in the apparent molecular weight of CKI delta from 55,000 to 49,000 as judged by polyacrylamide gel electro-phoresis in the presence of sodium dodecyl sulfate. Truncation of CKI delta by removal of the COOH-terminal 110 amino acids eliminated the ability of CS1 to activate or to increase electrophoretic mobility. Casein kinase I alpha, a 37-kDa isoform that lacks an extended COOH-terminal domain, was not activated by CS1 or the presence of heparin. However, a chimeric enzyme consisting of CKI alpha fused to the COOH-terminal domain of CKI delta was activated by both heparin and CS1. Analysis of the effects of CS1 on a series of CKI delta COOH-terminal truncation mutants identified an inhibitory region between His(317) and Pro(342), which contained six potential phosphorylation sites. From analysis of the specific activities of these truncation mutants, removal of the same region resulted in enzyme with a specific activity nearly 10-fold greater than wild-type. Thus, CKI delta activity can be regulated by phosphorylation of its COOH terminus, which may serve to create an autoinhibitory domain. This mechanism of regulation could have important consequences in vivo.