Division of Immunobiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.
The Biophysics Collaborative Access Team (BioCAT), Department of Biological Sciences, Illinois Institute of Technology, Chicago, IL, USA.
J Mol Biol. 2022 Aug 30;434(16):167708. doi: 10.1016/j.jmb.2022.167708. Epub 2022 Jun 28.
Staphylococcus epidermidis is a commensal bacterium on human skin that is also the leading cause of medical device-related infections. The accumulation-associated protein (Aap) from S. epidermidis is a critical factor for infection via its ability to mediate biofilm formation. The B-repeat superdomain of Aap is composed of 5 to 17 Zn-binding B-repeats, which undergo rapid, reversible assembly to form dimer and tetramer species. The tetramer can then undergo a conformational change and nucleate highly stable functional amyloid fibrils. In this study, multiple techniques including analytical ultracentrifugation (AUC) and small-angle X-ray scattering (SAXS) are used to probe a panel of B-repeat mutant constructs that assemble to distinct oligomeric states to define the structural characteristics of B-repeat dimer and tetramer species. The B-repeat region from Aap forms an extremely elongated conformation that presents several challenges for standard SAXS analyses. Specialized approaches, such as cross-sectional analyses, allowed for in-depth interpretation of data, while explicit-solvent calculations via WAXSiS allowed for accurate evaluation of atomistic models. The resulting models suggest mechanisms by which Aap functional amyloid fibrils form, illuminating an important contributing factor to recurrent staphylococcal infections.
表皮葡萄球菌是人体皮肤上的一种共生细菌，也是医疗器械相关感染的主要原因。表皮葡萄球菌的积累相关蛋白（Aap）是通过介导生物膜形成的能力成为感染的关键因素。Aap 的 B-重复超结构域由 5 到 17 个 Zn 结合的 B-重复组成，这些重复经历快速、可逆的组装形成二聚体和四聚体物种。然后，四聚体可以发生构象变化并引发高度稳定的功能淀粉样纤维。在这项研究中，使用了多种技术，包括分析超速离心（AUC）和小角 X 射线散射（SAXS），来探测一组组装成不同寡聚状态的 B-重复突变体构建体，以确定 B-重复二聚体和四聚体物种的结构特征。Aap 的 B-重复区形成了一种极其细长的构象，这给标准 SAXS 分析带来了一些挑战。特殊的方法，如横截面分析，允许对数据进行深入解释，而通过 WAXSiS 进行的明确溶剂计算则允许对原子模型进行准确评估。得到的模型表明了 Aap 功能淀粉样纤维形成的机制，阐明了复发性葡萄球菌感染的一个重要促成因素。
