An α-Helical Core Encodes the Dual Functions of the Chlamydial Protein IncA
An α-Helical Core Encodes the Dual Functions of the Chlamydial Protein IncA
复制标题
DOI：
10.1074/jbc.m114.592063
复制
发表时间：
2014-11-28
影响因子：
4.8
通讯作者：
Paumet, Fabienne
中科院分区：
文献类型：
--
作者：
Ronzone, Erik;Wesolowski, Jordan;Paumet, Fabienne
衣原体是一种细胞内细菌，在宿主细胞内的寄生虫隔室（内含物）内建立居所。衣原体包涵体与内溶酶体途径解偶联，并与细胞器融合以及相互融合。为此，衣原体使用III型分泌系统在包涵体表面表达蛋白质。这些蛋白质，称为Inc，位于宿主和病原体之间的界面，并执行衣原体生存所必需的功能。在这些Inc中，印加在保护包涵体免于溶酶体融合和诱导包涵体的同型融合中起关键作用。在印加内有两个与真核SNARE（可溶性N-乙基马来酰亚胺敏感因子附着受体）结构域同源的区域，称为SNARE样结构域1（SLD 1）和SNARE样结构域2（SLD 2）。使用多学科的方法，我们发现了印加的功能核心，保留了抑制SNARE介导的融合和促进衣原体包涵体的同型融合的能力。圆二色谱和分析超离心实验表明，这个核心区域几乎完全由α-螺旋组成，并在溶液中组装成稳定的同源二聚体。总之，我们建议，这两个印加功能编码在一个结构化的核心域，包括SLD 1和SLD 2的一部分。
Chlamydia is an intracellular bacterium that establishes residence within parasitophorous compartments (inclusions) inside host cells. Chlamydial inclusions are uncoupled from the endolysosomal pathway and undergo fusion with cellular organelles and with each other. To do so, Chlamydia expresses proteins on the surface of the inclusion using a Type III secretion system. These proteins, termed Incs, are located at the interface between host and pathogen and carry out the functions necessary for Chlamydia survival. Among these Incs, IncA plays a critical role in both protecting the inclusion from lysosomal fusion and inducing the homotypic fusion of inclusions. Within IncA are two regions homologous to eukaryotic SNARE (soluble N-ethylmaleimide-sensitive factor attachment receptor) domains referred to as SNARE-like domain 1 (SLD1) and SNARE-like domain 2 (SLD2). Using a multidisciplinary approach, we have discovered the functional core of IncA that retains the ability to both inhibit SNARE-mediated fusion and promote the homotypic fusion of Chlamydia inclusions. Circular dichroism and analytical ultracentrifugation experiments show that this core region is composed almost entirely of alpha-helices and assembles into stable homodimers in solution. Altogether, we propose that both IncA functions are encoded in a structured core domain that encompasses SLD1 and part of SLD2.