Structure of N-acetyl-β-D-glucosaminidase (GcnA) from the endocarditis pathogen Streptococcus gordonii and its complex with the mechanism-based inhibitor NAG-thiazoline
Structure of N-acetyl-β-D-glucosaminidase (GcnA) from the endocarditis pathogen Streptococcus gordonii and its complex with the mechanism-based inhibitor NAG-thiazoline
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DOI：
10.1016/j.jmb.2007.09.028
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发表时间：
2008-03-14
影响因子：
5.6
通讯作者：
Collyer, Charles A.
中科院分区：
文献类型：
--
作者：
Langley, David B.;Harty, Derek W. S.;Collyer, Charles A.
GcnA是一种来自格氏链球菌（Streptococcus gordonii）的N-乙酰基-β-D-氨基葡萄糖苷酶，通过使用硒代甲硫氨酸取代的蛋白质晶体的多波长反常色散定相来解析其晶体结构。GcnA是具有亚基的同源二聚体，每个亚基由三个结构域组成。C-末端α-螺旋结构域的结构先前未被观察到，并形成大的二聚化界面。N-末端结构域的折叠在所有结构相关的糖苷酶中观察到，尽管其功能未知。中心结构域具有包含活性位点的典型（β/α）（8）TIM桶折叠。该中心结构域的一级序列和结构将该酶鉴定为家族20糖苷酶。参与催化的关键残基在两种不同的晶体形式中具有不同的构象，这可能代表了酶的活性和非活性构象。这类糖苷水解酶的催化机制，其中底物，而不是酶提供裂解诱导亲核试剂，已被证实的结构GcnA与一个假定的反应中间体类似物，N-乙酰基-β-D-葡糖胺-噻唑啉复合。根据这些和其他家庭20结构的催化机制进行了讨论。皇冠版权所有（c）2007年出版的爱思唯尔有限公司保留所有权利。
The crystal structure of GcnA, an N-acetyl-beta-D-ghlCosaminidase from Streptococcus gordonii, was solved by multiple wavelength anomalous dispersion phasing using crystals of selenomethionine-substituted protein. GcnA is a homodimer with subunits each comprised of three domains. The structure of the C-terminal alpha-helical domain has not been observed previously and forms a large dimerisation interface. The fold of the N-terminal domain is observed in all structurally related glycosidases although its function is unknown. The central domain has a canonical (beta/alpha)(8) TIM-barrel fold which harbours the active site. The primary sequence and structure of this central domain identifies the enzyme as a family 20 glycosidase. Key residues implicated in catalysis have different conformations in two different crystal forms, which probably represent active and inactive conformations of the enzyme. The catalytic mechanism for this class of glycoside hydrolase, where the substrate rather than the enzyme provides the cleavage-inducing nucleophile, has been confirmed by the structure of GcnA complexed with a putative reaction intermediate analogue, N-acetyl-beta-D-glucosamine-thiazoline. The catalytic mechanism is discussed in light of these and other family 20 structures. Crown Copyright (c) 2007 Published by Elsevier Ltd. All rights reserved.