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首页> 外文期刊>Journal of bacteriology >X-Ray Structure and Site-Directed Mutagenesis Analysis of the Escherichia coli Colicin M Immunity Protein
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X-Ray Structure and Site-Directed Mutagenesis Analysis of the Escherichia coli Colicin M Immunity Protein

机译：大肠杆菌Colicin M免疫蛋白的X射线结构和定点诱变分析

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摘要

Colicin M (ColM), which is produced by some Escherichia coli strains to kill competitor strains from the same or related species, was recently shown to inhibit cell wall peptidoglycan biosynthesis through enzymatic degradation of its lipid II precursor. ColM-producing strains are protected from the toxin that they produce by coexpression of a specific immunity protein, named Cmi, whose mode of action still remains to be identified. We report here the resolution of the crystal structure of Cmi, which is composed of four β strands and four α helices. This rather compact structure revealed a disulfide bond between residues Cys31 and Cys107. Interestingly, these two cysteines and several other residues appeared to be conserved in the sequences of several proteins of unknown function belonging to the YebF family which exhibit 25 to 35% overall sequence similarity with Cmi. Site-directed mutagenesis was performed to assess the role of these residues in the ColM immunity-conferring activity of Cmi, which showed that the disulfide bond and residues from the C-terminal extremity of the protein were functionally essential. The involvement of DsbA oxidase in the formation of the Cmi disulfide bond is also demonstrated.
机译：最近发现，由某些大肠杆菌菌株产生的杀螨蛋白M（ColM）可杀死来自相同或相关物种的竞争菌株，该酶可通过酶降解其脂质II前体来抑制细胞壁肽聚糖的生物合成。通过共同表达一种名为Cmi的特异性免疫蛋白，可以保护产生ColM的菌株免受其产生的毒素的影响，该蛋白的作用方式仍有待确定。我们在这里报告Cmi的晶体结构的分辨率，该晶体由四个β链和四个α螺旋组成。这种相当紧凑的结构揭示了残基Cys31和Cys107之间的二硫键。有趣的是，这两个半胱氨酸和一些其他残基在属于YebF家族的功能未知的几种蛋白质的序列中似乎是保守的，这些蛋白质与Cmi的总体序列相似性为25％至35％。进行了定点诱变，以评估这些残基在赋予Cmi ColM免疫力的活性中的作用，这表明该蛋白C末端的二硫键和残基在功能上至关重要。还证明了DsbA氧化酶参与Cmi二硫键的形成。

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