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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Structural basis for alginate secretion across the bacterial outer membrane
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Structural basis for alginate secretion across the bacterial outer membrane

机译:藻酸盐分泌穿过细菌外膜的结构基础

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摘要

Pseudomonas aeruginosa is the predominant pathogen associated with chronic lung infection among cystic fibrosis patients. During colonization of the lung, P. aeruginosa converts to a mucoid phe-notype characterized by the overproduction of the exopolysacchar-ide alginate. Secretion of newly synthesized alginate across the outer membrane is believed to occur through the outer membrane protein AlgE. Here we report the 2.3 A crystal structure of AlgE, which reveals a monomeric 18-stranded (5-barrel characterized by a highly electropositive pore constriction formed by an arginine-rich conduit that likely acts as a selectivity filter for the negatively charged alginate polymer. Interestingly, the pore constriction is occluded on either side by extracellular loop L2 and an unusually long periplasmic loop, T8. In halide efflux assays, deletion of loop T8 (AT8-AlgE) resulted in a threefold increase in anion flux compared to the wild-type or AL2-AlgE supporting the idea that AlgE forms a transport pathway through the membrane and suggesting that transport is regulated by T8. This model is further supported by in vivo experiments showing that complementation of an algE deletion mutant with AT8-AlgE impairs alginate production. Taken together, these studies support a mechanism forexopolysaccharide export across the outer membrane that is distinct from the Wza-mediated translocation observed in canonical capsular polysacchar-ide export systems.
机译:铜绿假单胞菌是囊性纤维化患者中与慢性肺部感染相关的主要病原体。在肺部定殖过程中,铜绿假单胞菌转化为以胞外多糖-藻酸盐过量生产为特征的粘液性表型。据信新合成的藻酸盐通过外膜分泌是通过外膜蛋白AlgE发生的。在这里,我们报告了2.3 AlgE的晶体结构,该结构揭示了一个18链单体(5桶),其特征是富含精氨酸的导管形成了高度电正性的孔收缩,该孔可能充当带负电荷的藻酸盐聚合物的选择性过滤器。有趣的是,细胞外环L2和异常长的周质环T8阻塞了孔的狭窄处。在卤化物外排测定中,环T8(AT8-AlgE)的缺失导致阴离子通量比野生型增加了三倍。类型或AL2-AlgE支持AlgE形成通过膜的运输途径并暗示运输受T8调控的观点,该模型进一步得到体内实验的支持,该实验表明,algE缺失突变体与AT8-AlgE互补会损害藻酸盐的产生。综上所述,这些研究支持了外多糖跨外膜输出的机制,这与Wza介导的易位观察不同。 d在规范荚膜多糖出口系统中。

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  • 作者单位

    Molecular Structure and Function, The Hospital for Sick Children, Toronto, ON, Canada M5G 1X8,Department of Biochemistry, University of Toronto,Toronto, ON, Canada M5S 1A8;

    Institute of Molecular Biosciences, Massey University, Private Bag 11222, North Palmerston, New Zealand;

    Molecular Structure and Function, The Hospital for Sick Children, Toronto, ON, Canada M5G 1X8;

    Molecular Structure and Function, The Hospital for Sick Children, Toronto, ON, Canada M5G 1X8;

    Biology Department, Brookhaven National Laboratory, Upton, NY 11973-5000;

    Molecular Structure and Function, The Hospital for Sick Children, Toronto, ON, Canada M5G 1X8;

    Department of Microbiology and Immunology, McGuire Veterans Affairs Medical Center, Virginia Commonwealth University Medical Center, Richmond, VA 23298-0678;

    Department of Microbiology and Immunology, McGuire Veterans Affairs Medical Center, Virginia Commonwealth University Medical Center, Richmond, VA 23298-0678;

    Molecular Structure and Function, The Hospital for Sick Children, Toronto, ON, Canada M5G 1X8,Department of Physiology, University of Toronto, Toronto,ON, Canada M5S 1A8;

    Institute of Molecular Biosciences, Massey University, Private Bag 11222, North Palmerston, New Zealand;

    Molecular Structure and Function, The Hospital for Sick Children, Toronto, ON, Canada M5G 1X8,Department of Biochemistry, University of Toronto,Toronto, ON, Canada M5S 1A8;

  • 收录信息 美国《科学引文索引》(SCI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    biofilm; exopolysaccharide secretion; porin; virulence factor; uronic acids;

    机译:生物膜;外多糖分泌;孔蛋白;毒力因子;糖醛酸;

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