Anatomy of secretin binding to the Dickeya dadantii type II secretion system pilotin.
Anatomy of secretin binding to the Dickeya dadantii type II secretion system pilotin.
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DOI：
10.1107/s0907444913007658
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发表时间：
2013-08
期刊：
影响因子：
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通讯作者：
S. Rehman;S. Gu;V. Shevchik;R. Pickersgill
中科院分区：
文献类型：
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作者：
S. Rehman;S. Gu;V. Shevchik;R. Pickersgill
分泌素是革兰氏阴性细菌外膜上的一个大的多聚体通道家族，参与蛋白质输出。在Dickeya dadantii和许多其他致病细菌中，脂蛋白Pilotin针对外膜的分泌素亚基，允许组装一个功能性的II型分泌系统。在这里，报告了与其同源Pilotin结合的促胰液素亚单位的C-端肽的晶体结构。在溶液中，分泌素的这个C-末端区域是非结构化的。促胰液素多肽在与毛刺素结合时折叠，形成四个旋转的α-螺旋，紧密结合在毛刺素的第一个螺旋上，从而使分泌素螺旋中的疏水残基可以结合到毛刺素的疏水表面。分泌素螺旋与第四螺旋的第一部分平行结合。N-封端的天冬氨酸通过与螺旋分泌素多肽的螺旋偶极有利地相互作用而促进螺旋的形成和结合。这里描述的植物病原性达丹氏菌的分泌素-Pilotin复合体的结构是Pilotins Out-Puls家族中这种相互作用的范例，这对于几个强大的人类对手，包括肠出血性大肠杆菌和催产克雷伯氏菌的II型分泌系统的正确组装是必不可少的。
The secretins are a family of large multimeric channels in the outer membrane of Gram-negative bacteria that are involved in protein export. In Dickeya dadantii and many other pathogenic bacteria, the lipoprotein pilotin targets the secretin subunits to the outer membrane, allowing a functional type II secretion system to be assembled. Here, the crystal structure of the C-terminal peptide of the secretin subunit bound to its cognate pilotin is reported. In solution, this C-terminal region of the secretin is nonstructured. The secretin peptide folds on binding to the pilotin to form just under four turns of α-helix which bind tightly up against the first helix of the pilotin so that the hydrophobic residues of the secretin helix can bind to the hydrophobic surface of the pilotin. The secretin helix binds parallel to the first part of the fourth helix of the pilotin. An N-capping aspartate encourages helix formation and binding by interacting favourably with the helix dipole of the helical secretin peptide. The structure of the secretin-pilotin complex of the phytopathogenic D. dadantii described here is a paradigm for this interaction in the OutS-PulS family of pilotins, which is essential for the correct assembly of the type II secretion system of several potent human adversaries, including enterohaemorrhagic Escherichia coli and Klebsiella oxytoca.