The crystal structure of YdcE, a 4-oxalocrotonate tautomerase homologue from Escherichia coli, confirms the structural basis for oligomer diversity
The crystal structure of YdcE, a 4-oxalocrotonate tautomerase homologue from Escherichia coli, confirms the structural basis for oligomer diversity
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DOI：
10.1021/bi020271h
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发表时间：
2002-10-08
期刊：
影响因子：
2.9
通讯作者：
Whitman, CP
中科院分区：
文献类型：
--
作者：
Almrud, JJ;Kern, AD;Whitman, CP
互变异构酶超家族由三个主要家族组成，以4-巴豆酸互变异构酶（4-OT）、5-（羧甲基）-2-羟基粘康酸异构酶（CHMI）和巨噬细胞迁移抑制因子（MIF）为代表。这个超家族的成员是结构上同源的蛋白质，由一个简单的β-α-β折叠构成，它们具有一个关键的机制特征;它们使用氨基末端的脯氨酸作为酮-烯醇互变异构化的一般基础，脯氨酸具有异常低的pK（a）。现在已经使用PSI-BLAST鉴定了4-OT家族的几个新成员，并根据多序列比对和关键催化和结构残基的保守性将其分为五个亚家族。亚家族5的成员，包括来自大肠杆菌的命名为YdcE的假设蛋白质，预计不会形成六聚体。YdcE的晶体结构已被确定为1.35埃的分辨率，并确认它是一个二聚体。此外，YdcE与（E）-2-氟-对羟基肉桂酸酯的复合物，被鉴定为该酶的有效竞争性抑制剂，以及N-（2-羟乙基）哌嗪-N '-2-乙磺酸（HEPES）和苯甲酸酯也被呈现。后者的晶体结构揭示了活性位点的位置，并建议所观察到的YdcE催化的互变异构反应的机制。YdcE的二聚体排列代表了4-OT家族中的一种新结构，并证明了4-OT家族中以前未报道的结构多样性。
The tautomerase superfamily consists of three major families represented by 4-oxalocrotonate tautomerase (4-OT), 5-(carboxymethyl)-2-hydroxymuconate isomerase (CHMI), and macrophage migration inhibitory factor (MIF). The members of this superfamily are structurally homologous proteins constructed from a simple beta-alpha-beta fold that share a key mechanistic feature; they use an amino-terminal proline, which has an unusually low pK(a), as the general base in a keto-enol tautomerization. Several new members of the 4-OT family have now been identified using PSI-BLAST and categorized into five subfamilies on the basis of multiple-sequence alignments and the conservation of key catalytic and structural residues. The members of subfamily 5, which includes a hypothetical protein designated YdcE from Escherichia coli, are predicted not to form hexamers. The crystal structure of YdcE has been determined to 1.35 Angstrom resolution and confirms that it is a dimer. In addition, YdcE complexed with (E)-2-fluoro-p-hydroxycinnamate, identified as a potent competitive inhibitor of this enzyme, as well as N-(2-hydroxyethyl)piperazine-N'-2-ethanesulfonic acid (HEPES) and benzoate are also presented. These latter crystal structures reveal the location of the active site and suggest a mechanism for the observed YdcE-catalyzed tautomerization reaction. The dimeric arrangement of YdcE represents a new structure in the 4-OT family and demonstrates structural diversity within the 4-OT family not previously reported.