Structural and Functional Studies of the Streptococcal Fibrillar Adhesin CshA
Structural and Functional Studies of the Streptococcal Fibrillar Adhesin CshA
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链球菌原纤维粘附素 CshA 的结构和功能研究
DOI：
10.1096/fasebj.2018.32.1_supplement.118.1
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发表时间：
2018
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Back C
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作者：
Back C
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，戈登链球菌是一种口腔共生性和机会性病原体。CSHA与其他蛋白质的序列同源性较低，表明其具有潜在的新的结构特征。我们的研究表明，CSHA的N-末端区域形成了纤维的功能头部，末端有一个无序的部分。C-末端区域由17个重复区块组成，每个重复区块由~99个氨基酸残基(3个不完整)组成，形成一个长而灵活的柄，呈现出细菌细胞表面远端的潜在结合域。在这项研究中，我们提出了CSHA的结构分析，源于X射线结晶学，核磁共振，SAXS和互补的生物物理方法的组合。这些数据表明，CSHA具有一种以前没有报道的细菌细胞表面粘附素的新结构，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是促进的。在宿主内的多个地点进行戈多尼亚殖民。然而，这两种蛋白质如何相互作用的分子细节以前还没有被研究过。在体外结合研究中，支持迄今为止未报道的CSHA与FN结合的两态“捕捉钳制”机制。CSHA无序的N-末端结构域通过形成一个快速组装但也很容易解离的前复合体来“捕捉”FN，使其邻近的配体结合结构域能够将两个多肽紧紧地“夹住”在一起。这项研究提出了一种通过细菌粘附素结合靶标的新范式，其鉴定将为未来开发靶标的抗粘附剂提供信息。支持或资助信息这项工作得到了美国国立卫生研究院DE016690(对H.F.J.和R.J.L.)的部分资助和DE012505(授予R.J.L.)，生物技术和生物科学研究理事会授予BB/I006478/1(授予P.R.)，以及皇家学会大学研究奖学金奖UF080534(授予P.R.)。内容完全由作者负责，并不一定代表美国国立卫生研究院的官方观点。本文摘要来自2018年实验生物学会议。FASE期刊上没有发表与这篇摘要相关的全文文章。
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. Due to their size and often elaborate multi‐domain 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 byStreptococcus gordonii, an oral commensal and opportunistic human pathogen. CshA has a low sequence identity to other proteins, indicating potentially novel structural characteristics.Our studies indicate that the N‐terminal region of CshA forms a functional head of the fibril, with a disordered portion at the tip. The C‐terminal region comprises 17 repeat blocks, each of ~99 aa residues (three incomplete), which form a long, flexible stalk, presenting the potential binding domain distal from the bacterial cell surface. In this study we present a structural analysis of CshA, derived from a combination of X‐ray crystallography, NMR, SAXS, and complementary biophysical methods. The data suggest that CshA has a novel structure not previously reported for bacterial cell surface adhesins.CshA binds the high‐molecular‐weight glycoprotein fibronectin (Fn)viathe N‐terminal non‐repetitive region, and this protein‐protein interaction has been proposed to promoteS. gordoniicolonization at multiple sites within the host. However, the molecular details of how these two proteins interact had not previously been investigated.In vitrobinding studies support a hitherto unreported two‐state ‘catch‐clamp’ mechanism of Fn binding by CshA. 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 neighbouring 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 towards the development of anti‐adhesive agents that targetS. gordoniiand related streptococci.Support or Funding InformationThis work was supported in part by National Institutes of Health grants DE016690 (to H. F. J. and R. J. L.) and DE012505 (to R. J. L.), Biotechnology and Biological Sciences Research Council Grant BB/I006478/1 (to P. R. R.), and Royal Society University Research Fellowship Award UF080534 (to P. R. R.). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published inThe FASEB Journal.