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首页> 外文期刊>Journal of Molecular Biology >Crystal Structure of IscA, an Iron-sulfur Cluster Assembly Protein from Escherichia coli.
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Crystal Structure of IscA, an Iron-sulfur Cluster Assembly Protein from Escherichia coli.

机译：IscA的晶体结构，这是一种来自大肠杆菌的铁硫簇装配蛋白。

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摘要

IscA, an 11 kDa member of the hesB family of proteins, binds iron and [2Fe-2S] clusters, and participates in the biosynthesis of iron-sulfur proteins. We report the crystal structure of the apo-protein form of IscA from Escherichia coli to a resolution of 2.3A. The crystals belong to the space group P3(2)21 and have unit cell dimensions a=b=66.104A, c=150.167A (alpha=beta=90 degrees, gamma=120 degrees ). The structure was solved using single-wavelength anomalous dispersion (SAD) phasing of a selenomethionyl derivative, and the IscA model was refined to R=21.4% [Formula: see text] IscA exists as an (alpha(1)alpha(2))(2) homotetramer with the (alpha(1)alpha(2)) dimer comprising the asymmetric unit. Cys35, implicated in Fe-S cluster assembly, is located in a central cavity formed at the tetramer interface with the gamma-sulfur atoms of residues from the alpha(1) and alpha(2)' monomers (and alpha(1)'alpha(2)) positioned close to one another (?7A). C-terminal residues 99-107 are disordered, and the exact positions of Cys99 and Cys101 could not be determined. However, computer modeling of C-terminal residues in the tetramer suggests that Cys99 and Cys101 in the alpha(1) monomer and those of the alpha(1)' monomer (or alpha(2) and alpha(2)') are positioned sufficiently close to coordinate [2Fe-2S] clusters between the two dimers, whereas this is not possible within the (alpha(1)alpha(2)) or (alpha(1)'alpha(2)') dimer. This symmetrical arrangement allows for binding of two [2Fe-2S] clusters on opposite sides of the tetramer. Modeling further reveals that Cys101 is positioned sufficiently close to Cys35 to allow Cys35 to participate in cluster assembly, formation, or transfer.
机译：IscA是hesB蛋白质家族的11 kDa成员，结合铁和[2Fe-2S]簇，并参与铁硫蛋白质的生物合成。我们报告了来自大肠杆菌的IscA载脂蛋白形式的晶体结构，分辨率为2.3A。晶体属于空间群P3（2）21，并且具有晶胞尺寸a = b = 66.104A，c = 150.167A（α=β= 90度，伽马= 120度）。使用硒代甲硫酰基衍生物的单波长异常色散（SAD）相位解决了结构问题，并将IscA模型细化为R = 21.4％[公式：参见文本] IscA以（alpha（1）alpha（2））的形式存在。 （2）具有（α（1）α（2））二聚体的同四聚体包含不对称单元。与Fe-S簇组装有关的Cys35位于四聚体界面处形成的中心腔中，该四聚体界面与来自alpha（1）和alpha（2）'单体（和alpha（1）'alpha的残基的gamma硫原子（2））彼此靠近放置（？7A）。 C端残基99-107是无序的，并且不能确定Cys99和Cys101的确切位置。但是，对四聚体中C端残基的计算机建模表明，alpha（1）单体中的Cys99和Cys101和alpha（1）'单体（或alpha（2）和alpha（2）'）的残基位置足够两个二聚体之间接近于[2Fe-2S]坐标簇，而在（alpha（1）alpha（2））或（alpha（1）'alpha（2）'）二聚体中这是不可能的。这种对称排列允许在四聚体的相对侧结合两个[2Fe-2S]簇。建模进一步揭示，Cys101的位置足够接近Cys35，以允许Cys35参与簇的组装，形成或转移。

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