Type II protein secretion in gram-negative pathogenic bacteria:: The study of the structure/secretion relationships of the cellulase CeI5 (formerly EGZ) from Erwinia chrysanthemi
Type II protein secretion in gram-negative pathogenic bacteria:: The study of the structure/secretion relationships of the cellulase CeI5 (formerly EGZ) from Erwinia chrysanthemi
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DOI：
10.1006/jmbi.2001.4787
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发表时间：
2001-07-27
影响因子：
5.6
通讯作者：
Barras, F
中科院分区：
文献类型：
--
作者：
Chapon, V;Czjzek, M;Barras, F
菊欧文氏菌（Erwinia chrysanthemi）是一种革兰氏阴性植物病原体，通过II型分泌途径（简称Out）分泌纤维素酶Cel5（以前称为EGZ）。 Cel5 由两个结构域组成，一个大的 N 端催化结构域（390 个氨基酸残基）和一个小的 C 端纤维素结合结构域（62 个氨基酸残基），由连接子区域分隔。诱变和结构分析的结合使我们能够研究 Cel5 催化结构域的结构/分泌关系。催化域的 3D 结构通过分子替换以 2.3 埃分辨率解析。 Cel5 表现出 (beta/alpha)(8) 结构折叠和两个额外的桶特征。我们之前基于 tRNA 介导的抑制的基因研究使我们能够预测分子中与结构和催化相关的重要位置。值得注意的是，与现有的结构信息相比，所有预测都被证明是正确的。位于催化结构域核心的 Arg57 的突变使我们能够测试结构修饰对分泌效率的影响。结果表明，保密性对折叠施加了非常强的限制。特别是，精氨酸到组氨酸的突变产生了一种折叠成稳定构象的物种，该构象接近但不同于野生型，但野生型是不可分泌的。我们讨论了周质中蛋白质折叠、通往细胞外部的过程与分泌信息的呈现之间的关系。我们建议为 II 型分泌外蛋白选择不同的解决方案，以满足它们与各自分泌机制相互作用所施加的限制。我们认为，进化压力导致不同的 II 型外蛋白适应不同的分泌基序。 (C) 2001 年学术出版社。
Erwinia chrysanthemi, a Gram-negative plant pathogen, secretes the cellulase Cel5 (formerly EGZ) via the type II secretion pathway (referred to as Out). Cel5 is composed of two domains, a large N-terminal catalytic domain (390 amino acid residues) and a small C-terminal cellulose-binding domain (62 amino acid residues) separated by a linker region. A combination of mutagenesis and structural analysis permitted us to investigate the structure/secretion relationships with respect to the catalytic domain of Cel5. The 3D structure of the catalytic domain was solved by molecular replacement at 2.3 Angstrom resolution. Cel5 exhibits the (beta/alpha)(8) structural fold and two extra-barrel features. Our previous genetic study based upon tRNA-mediated suppression allowed us to predict positions of importance in the molecule in relation to structure and catalysis. Remarkably, all of the predictions proved to be correct when compared with the present structural information. Mutations of Arg57, which is located at the heart of the catalytic domain, allowed us to test the consequences of structural modifications on the secretion efficiency. The results revealed that secretability imposes remarkably strong constraints upon folding. In particular, an Arg-to-His mutation yielded a species that folded to a stable conformation close to, but distinct from the wild-type, which however was not secretable. We discuss the relationships between folding of a protein in the periplasm, en route to the cell exterior, and presentation of secretion information. We propose that different solutions have been selected for type II secreted exoproteins in order to meet the constraints imposed by their interaction with their respective secretion machineries. We propose that evolutionary pressure has led to the adaptation of different secretion motifs for different type II exoproteins. (C) 2001 Academic Press.