Crystal structure of a C-terminal deletion mutant of human protein kinase CK2 catalytic subunit
Crystal structure of a C-terminal deletion mutant of human protein kinase CK2 catalytic subunit
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DOI：
10.1016/s0022-2836(03)00638-7
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发表时间：
2003-07-25
影响因子：
5.6
通讯作者：
Niefind, K
中科院分区：
文献类型：
--
作者：
Ermakova, I;Boldyreff, B;Niefind, K
蛋白激酶CK 2（以前称为：酪蛋白激酶2）是一种异源四聚体酶，由两个独立的催化链（CK 2 α）和两个非催化亚基（CK 2 β）的稳定二聚体组成。CK 2 α是真核生物蛋白激酶超家族的一个高度保守的成员。解析了人CK 2 α的C-末端缺失突变体的晶体结构，并将其精细化至2.5埃分辨率。在晶体中，CK 2 α突变体作为单体存在，与CK 2全酶中亚基的组织一致。精细结构显示的螺旋alphaC和激活段，两个主要的区域的构象可塑性和监管的重要性，在真核蛋白激酶，在活性构象稳定的广泛接触的N-末端段。这种排列与酶的组成活性一致。通过分离形式的人CK 2 α的结构叠加并嵌入人CK 2全酶中，连接链β 4和β 5的环和ATP-bind.ing环被鉴定为结构变异性的元件。这种结构比较表明ATP结合环可能是非催化性CK 2 β二聚体调节CK 2 α活性的关键区域。发现β 4/β 5环处于闭合构象，而CK 2全酶的CK 2 α亚基则处于开放构象。由于空间原因，具有这种闭合β 4/β 5环构象的CK 2 α单体不能以常见方式结合CK 2 β二聚体，这表明存在保护CK 2 α免于整合到CK 2全酶复合物中的机制。这一观察结果与越来越多的证据一致，即CK 2 α单体和CK 2 β二聚体可以独立于CK 2全酶存在于体内，并且可能具有它们自己的生理作用。(C)2003 Elsevier Ltd.保留所有权利。
Protein kinase CK2 (formerly called: casein kinase 2) is a heterotetrameric enzyme composed of two separate catalytic chains (CK2alpha) and a stable dimer of two non-catalytic subunits (CK2P). CK2alpha is a highly conserved member of the superfamily of eukaryotic protein kinases. The crystal structure of a C-terminal deletion mutant of human CK2alpha was solved and refined to 2.5 Angstrom resolution. In the crystal the CK2alpha mutant exists as a monomer in agreement with the organization of the subunits in the CK2 holoenzyme. The refined structure shows the helix alphaC and the activation segment, two main regions of conformational plasticity and regulatory importance in eukaryotic protein kinases, in active conformations stabilized by extensive contacts to the N-terminal segment. This arrangement is in accordance with the constitutive activity of the enzyme. By structural superimposition of human CK2alpha in isolated form and embedded in the human CK2 holoenzyme the loop connecting the strands beta4 and beta5 and the ATP-bind.ing loop were identified as elements of structural variability. This structural comparison suggests that the ATP-binding loop may be the key region by which the non-catalytic CK2beta dimer modulates the activity of CK2alpha. The beta4/beta5 loop was found in a closed conformation in contrast to the open conformation observed for the CK2alpha subunits of the CK2 holoenzyme. CK2alpha monomers with this closed beta4/beta5 loop conformation are unable to bind CK2beta dimers in the common way for sterical reasons, suggesting a mechanism to protect CK2alpha from integration into CK2 holoenzyme complexes. This observation is consistent with the growing evidence that CK2alpha monomers and CK2beta dimers can exist in vivo independently from the CK2 holoenzyme and may possess physiological roles of their own. (C) 2003 Elsevier Ltd. All rights reserved.