The Streptococcus gordonii Adhesin CshA Protein Binds Host Fibronectin via a Catch-Clamp Mechanism
The Streptococcus gordonii Adhesin CshA Protein Binds Host Fibronectin via a Catch-Clamp Mechanism
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DOI：
10.1074/jbc.m116.760975
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发表时间：
2017-02-03
影响因子：
4.8
通讯作者：
Race, Paul R.
中科院分区：
文献类型：
--
作者：
Back, Catherine R.;Sztukowska, Maryta N.;Race, Paul R.
细菌附着在生物或非生物表面是寄主定植的先决条件，是微生物致病的重要一步。这种附着是由细胞表面的细菌粘附素促进的。由于它们的大小和通常复杂的多结构域结构，这些多肽是详细结构和功能表征的具有挑战性的目标。多功能纤维粘附素CSHA介导与宿主分子和其他微生物的结合，是戈登链球菌定植的重要决定因素，戈登链球菌是一种动物和人类的口腔共生和条件致病菌。CSHA通过N端的非重复区域与大分子糖蛋白纤维连接蛋白(FN)结合，这种蛋白质-蛋白质相互作用被认为促进了戈登葡萄球菌在宿主内的多个位置的定植。然而，这两种蛋白质如何相互作用的分子细节尚未确定。在这里，我们提出了CSHA的FN结合N-末端区域的结构描述，源于X射线结晶学、小角X射线散射和互补生物物理方法的组合。体外结合研究支持一种以前未见报道的CSHA与FN结合的两态捕获钳制机制，在该机制中，CSHA无序的N-末端结构域通过形成一个快速组装但也容易解离的前复合体来捕获FN，使其邻近的配体结合域能够将两个多肽紧密地夹在一起。这项研究提出了一种通过细菌粘附素进行靶向结合的新范式，其鉴定将为未来开发针对戈登氏链球菌和相关链球菌的抗粘附剂提供信息。
Adherence of bacteria to biotic or abiotic surfaces is a prerequisite for host colonization and represents an important step in microbial pathogenicity. This attachment is facilitated by bacterial adhesins at the cell surface. Because of their size and often elaborate multidomain architectures, these polypeptides represent challenging targets for detailed structural and functional characterization. The multifunctional fibrillar adhesin CshA, which mediates binding to both host molecules and other microorganisms, is an important determinant of colonization by Streptococcus gordonii, an oral commensal and opportunistic pathogen of animals and humans. CshA binds the high-molecular-weight glycoprotein fibronectin (Fn) via an N-terminal non-repetitive region, and this protein-protein interaction has been proposed to promote S. gordonii colonization at multiple sites within the host. However, the molecular details of how these two proteins interact have yet to be established. Here we present a structural description of the Fn binding N-terminal region of CshA, derived from a combination of X-ray crystallography, small angle X-ray scattering, and complementary biophysical methods. In vitro binding studies support a previously unreported two-state catch-clamp mechanism of Fn binding by CshA, in which the disordered N-terminal domain of CshA acts to catch Fn, via formation of a rapidly assembled but also readily dissociable pre-complex, enabling its neighboring ligand binding domain to tightly clamp the two polypeptides together. This study presents a new paradigm for target binding by a bacterial adhesin, the identification of which will inform future efforts toward the development of anti-adhesive agents that target S. gordonii and related streptococci.