Crystal structure of nitrile hydratase reveals a novel iron centre in a novel fold
Crystal structure of nitrile hydratase reveals a novel iron centre in a novel fold
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DOI：
10.1016/s0969-2126(97)00223-2
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发表时间：
1997-05-15
期刊：
影响因子：
5.7
通讯作者：
Lindqvist, Y
中科院分区：
文献类型：
--
作者：
Huang, WJ;Jia, J;Lindqvist, Y
背景：腈水合酶是一类特殊的金属酶，催化腈类化合物水合生成酰胺。它们被用作丙烯酰胺生产中的生物催化剂，这是为数不多的商业规模生物工艺之一，以及用于从废物流中去除腈的环境修复。腈水合酶由两个亚基α和β组成，并且它们每个杯单位含有一个铁原子。我们已经确定了光活化的含铁腈水合酶的晶体结构，从红球菌属R312到2.65埃分辨率作为第一步，在阐明其催化mechanism.Results：的a亚基由一个长的N-末端臂和C-末端结构域，形成一个新的折叠。这种折叠可以被描述为四层结构，α-β-β-α，β链之间具有不寻常的连接性。β亚基还包含一个长的N-末端延伸，一个螺旋结构域和一个折叠成β卷的C-末端结构域。这两个亚基形成一个紧密的异源二聚体，是酶的功能单位。活性位点位于亚基-亚基界面处的空腔中。铁中心是由残基从α亚基只有三个半胱氨酸硫醇盐和两个主链酰胺氮原子ligand.Conclusions：腈水合酶包含一个新的铁中心与以前没有观察到的蛋白质的结构，它类似于血红素和Fe-S蛋白质的铁中心的杂交。两自旋电子配置推测部分结果从两个Fe-酰胺氮键。该结构与在催化反应中起刘易斯酸作用的金属离子一致。
Background: Nitrile hydratases are unusual metalloenzymes that catalyze the hydration of nitriles to their corresponding amides. They are used as biocatalysts in acrylamide production, one of the few commercial scale bioprocesses, as well as in environmental remediation for the removal of nitriles from waste streams. Nitrile hydratases are composed of two subunits, alpha and beta, and they contain one iron atom per cup unit. We have determined the crystal structure of photoactivated iron-containing nitrile hydratase from Rhodococcus sp. R312 to 2.65 Angstrom resolution as a first step in the elucidation of its catalytic mechanism.Results: The a subunit consists of a long N-terminal arm and a C-terminal domain that forms a novel fold. This fold can be described as a four layered structure, alpha-beta-beta-alpha, with unusual connectivities between the beta strands. The beta subunit also contains a long N-terminal extension, a helical domain, and a C-terminal domain that folds into a beta roll. The two subunits form a tight heterodimer that is the functional unit of the enzyme. The active site is located in a cavity at the subunit-subunit interface. The iron centre is formed by residues from the alpha subunit only-three cysteine thiolates and two mainchain amide nitrogen atoms are ligands.Conclusions: Nitrile hydratases contain a novel iron centre with a structure not previously observed in proteins; it resembles a hybrid of the iron centres of heme and Fe-S proteins. The tow-spin electronic configuration presumably results in part from two Fe-amide nitrogen bonds. The structure is consistent with the metal ion having a role as a Lewis acid in the catalytic reaction.