Structure of thiocyanate hydrolase: A new nitrile hydratase family protein with a novel five-coordinate cobalt(III) center
Structure of thiocyanate hydrolase: A new nitrile hydratase family protein with a novel five-coordinate cobalt(III) center
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DOI：
10.1016/j.jmb.2006.12.011
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发表时间：
2007-03-09
影响因子：
5.6
通讯作者：
Odaka, Masafumi
中科院分区：
文献类型：
--
作者：
Arakawa, Takatoshi;Kawano, Yoshiaki;Odaka, Masafumi
硫氰化物水解酶（SCNase）是一种含钴（III）的酶，催化硫氰酸盐降解为硫化羰和氨。我们以2.0埃的分辨率确定了载脂蛋白和天然SCNs的晶体结构。两种形式的SCNs都具有保守的异十二聚体结构（α β γ）（4）。四种α β γ异源三聚体在结构上是等同的。其中一种α-β-γ异源三聚体由核心结构域和β-N结构域组成，β-N结构域位于分子的中心，通过新颖的四元界面将异源三聚体连接起来。在载脂蛋白和天然SCNase中，核心结构域在铁和钴型腈水合酶（NHase）之间结构保守。天然SCNase具有后修饰的半胱氨酸配体，γ Cys 131-SO2 H和γ Cys 133-SOH样NHases。然而，低自旋钴（III）被发现是在扭曲的四方锥几何形状，这是以前没有报道过的任何蛋白质。底物结合口袋的大小以及静电性质在电荷分布和底物可及性方面与NHase完全不同，这合理地解释了SCNase和NHase之间底物偏好的差异。(c)2006爱思唯尔有限公司保留所有权利。
Thiocyanate hydrolase (SCNase) of Thiobacillus thioparus THI115 is a cobalt (III)-containing enzyme catalyzing the degradation of thiocyanate to carbonyl sulfide and ammonia. We determined the crystal structures of the apo- and native SCNases at a resolution of 2.0 angstrom. SCNases in both forms had a conserved hetero-dodecameric structure, (alpha beta gamma)(4). Four alpha beta gamma heterotrimers were structurally equivalent. One a alpha beta gamma hetero-trimer was composed of the core domain and the beta N domain, which was located at the center of the molecule and linked the hetero-trimers with novel quaternary interfaces. In both the apo- and native SCNases, the core domain was structurally conserved between those of iron and cobalt-types of nitrile hydratase (NHase). Native SCNase possessed the post-translationally modified cysteine ligands, gamma Cys131-SO2H and gamma Cys133-SOH like NHases. However, the low-spin cobalt(III) was found to be in the distorted square-pyramidal geometry, which had not been reported before in any protein. The size as well as the electrostatic properties of the substrate-binding pocket was totally different from NHases with respect to the charge distribution and the substrate accessibility, which rationally explains the differences in the substrate preference between SCNase and NHase. (c) 2006 Elsevier Ltd. All rights reserved.