The 1.9 Å crystal structure of alanine racemase from Mycobacterium tuberculosis contains a conserved entryway into the active site
The 1.9 Å crystal structure of alanine racemase from Mycobacterium tuberculosis contains a conserved entryway into the active site
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DOI：
10.1021/bi0486583
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发表时间：
2005-02-08
期刊：
影响因子：
2.9
通讯作者：
Krause, KL
中科院分区：
文献类型：
--
作者：
LeMagueres, P;Im, H;Krause, KL
报道了结核分枝杆菌丙氨酸外消旋酶(ALR(Mtb))在1.9埃分辨率下的晶体结构。在我们的结构中，ALR(Mtb)被发现是由两个结晶学上不同的单体形成的二聚体，每个单体包含384个残基。每个单体的结构域组成类似于芽孢杆菌和假单胞菌丙氨酸消旋酶，并且在N-末端包括一个α/β-桶和一个主要由β-链组成的C-末端。这两个结构域之间的铰链角度对于ALR(Mtb)是唯一的，但活性中心的几何构型是保守的。在ALR(Mtb)中，PLP辅助因子通过与Lys42的内醛胺键共价结合到蛋白质上。在其活性部位没有观察到客体底物，尽管在酶的活性部位口袋中观察到了一些残余电子密度。在其他已知的丙氨酸外消旋酶的背景下，对活性部位口袋的分析使我们能够提议将在结合口袋入口处发现的保守残基作为正在进行的结构辅助药物设计工作的额外靶点。此外，正如在其他丙氨酸外消旋酶结构中观察到的那样，PLP采用的构象显著扭曲了PLP环和内部乙二胺键之间的扩展共轭体系的平面性。
We report the crystal structure of alanine racemase from Mycobacterium tuberculosis (Alr(Mtb)) at 1.9 Angstrom resolution. In our structure, Alr(Mtb) is found to be a dimer formed by two crystallographically different monomers, each comprising 384 residues. The domain makeup of each monomer is similar to that of Bacillus and Pseudomonas alanine racemases and includes both an alpha/beta-barrel at the N-terminus and a C-terminus primarily made of beta-strands. The hinge angle between these two domains is unique for Alr(Mtb), but the active site geometry is conserved. In Alr(Mtb), the PLP cofactor is covalently bound to the protein via an internal aldimine bond with Lys42. No guest substrate is noted in its active site, although some residual electron density is observed in the enzyme's active site pocket. Analysis of the active site pocket, in the context of other known alanine racemases, allows us to propose the inclusion of conserved residues found at the entrance to the binding pocket as additional targets in ongoing structure-aided drug design efforts. Also, as observed in other alanine racemase structures, PLP adopts a conformation that significantly distorts the planarity of the extended conjugated system between the PLP ring and the internal aldimine bond.