X-RAY STRUCTURE DETERMINATION OF TELOKIN, THE C-TERMINAL DOMAIN OF MYOSIN LIGHT CHAIN KINASE, AT 2.8 ANGSTROM RESOLUTION
X-RAY STRUCTURE DETERMINATION OF TELOKIN, THE C-TERMINAL DOMAIN OF MYOSIN LIGHT CHAIN KINASE, AT 2.8 ANGSTROM RESOLUTION
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DOI：
10.1016/0022-2836(92)90226-a
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发表时间：
1992-10-05
影响因子：
5.6
通讯作者：
RAYMENT, I
中科院分区：
文献类型：
--
作者：
HOLDEN, HM;ITO, M;RAYMENT, I
telokin是一种酸性蛋白质，与火鸡砂囊平滑肌肌球蛋白轻链激酶的C-末端部分相同，其三维结构已在2.8 μ m分辨率下测定，并对30 μ m至2.8 μ m的所有测量X射线数据进行了晶体学R因子为19.5%的修正。研究中使用的晶体属于空间群P3 2 2 1，每个不对称单元一个分子，晶胞尺寸为a= B= 64· 4 A和c= 50· 6 A。Telokin含有154个氨基酸残基，其中103个在电子密度图中可见。telokin的整个分子折叠由七股反平行的β-折叠片组成，这些折叠片缠绕形成桶。在N末端还存在不参与β折叠形成的8个氨基酸残基的延伸尾部。β-桶可以简单地设想为两层β-折叠，几乎彼此平行，其中一层含有四条β-链，另一层含有三条β-链。这种类型的β-桶，如在telokin中所见，首先在免疫球蛋白片段Fc的CH 2结构域中观察到。端粒蛋白是一种细胞内蛋白，因此不含通常在免疫球蛋白恒定结构域中观察到的β链B和F之间的二硫键。然而，它确实含有两个半胱氨酸氨基酸残基（Cys 63和Cys 115），其位于与免疫球蛋白恒定结构域中形成二硫键的那些在结构上相同的位置。
The three-dimensional structure of telokin, an acidic protein identical to the C-terminal portion of smooth muscle myosin light chain kinase from turkey gizzard, has been determined at 2· 8 Å resolution and refined to a crystallographic R-factor of 19· 5% for all measured X-ray data from 30 Å to 2· 8 Å. Crystals used in the investigation belonged to the space group P3 2 21, with one molecule per asymmetric unit and unit cell dimensions of a= b= 64· 4 A ̊ and c= 50· 6 A ̊. Telokin contains 154 amino acid residues, 103 of which were visible in the electron density map. The overall molecular fold of telokin consists of seven strands of antiparallel β-pleated sheet that wrap around to form a barrel. There is also an extended tail of eight amino acid residues at the N terminus that does not participate in β-sheet formation. The β-barrel can be simply envisioned as two layers of β-sheet, nearly parallel to one another, with one layer containing four and the other three β-strands. This type of β-barrel, as seen in telokin, was first observed for the CH2 domain of an immunoglobulin fragment Fc. Telokin is an intracellular protein and, as such, does not contain the disulphide linkage between β-strands B and F normally observed in the immunoglobulin constant domains. It does, however, contain two cysteine amino acid residues (Cys63 and Cys115) that are situated at structurally identical positions to those forming the disulphide linkage in the immunoglobulin constant domain.