The accumulation-associated protein (Aap) is the primary determinant of Staphylococcus epidermidis device-related infections. The B-repeat superdomain is responsible for intercellular adhesion that leads to the development of biofilms occurring in such infections. It was recently demonstrated that Zn-induced B-repeat assembly leads to formation of functional amyloid fibrils, which offer strength and stability to the biofilm. Rigorous biophysical studies of Aap B-repeats from S. epidermidis strain RP62A revealed Zn-induced assembly into stable, reversible dimers and tetramers, prior to aggregation into amyloid fibrils. Genetic manipulation is not tractable for many S. epidermidis strains, including RP62A; instead, many genetic studies have used strain 1457. Therefore, to better connect findings from biophysical and structural studies of B-repeats to in vivo studies, the B-repeat superdomain from strain 1457 was examined. Differences between the B-repeats from strains RP62A and 1457 include the number of B-repeats, which has been shown to play a critical role in assembly into amyloid fibrils, as well as the distribution of consensus and variant B-repeat subtypes, which differ in assembly competency and thermal stability. Detailed investigation of the Zn-induced assembly of the full B-repeat superdomain from strain 1457 was conducted using analytical ultracentrifugation. Whereas the previous construct from RP62A (Brpt5.5) formed a stable tetramer prior to aggregation, Brpt6.5 from 1457 forms extremely large stable species on the order of ≈28-mers, prior to aggregation into similar amyloid fibrils. Our data suggest that both assembly pathways may proceed through the same mechanism of dimerization and tetramerization, and both conclude with the formation of amyloid-like fibrils. Discussion of assembly behavior of B-repeats from different strains and of different length is provided with considerations of biological implications.

中文翻译：

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来自表皮葡萄球菌菌株 1457 的完整 B 重复序列超结构域的组装景观


积累相关蛋白 （Aap） 是表皮葡萄球菌装置相关感染的主要决定因素。B 重复序列超结构域负责细胞间粘附，导致在此类感染中发生生物膜的形成。最近证明，Zn 诱导的 B 重复序列组装导致功能性淀粉样蛋白原纤维的形成，从而为生物膜提供强度和稳定性。对表皮葡萄球菌菌株 RP62A 的 Aap B 重复序列的严格生物物理研究表明，Zn 诱导组装成稳定、可逆的二聚体和四聚体，然后聚集成淀粉样蛋白原纤维。许多表皮葡萄球菌菌株的基因操作无法处理，包括 RP62A;相反，许多遗传研究都使用了 1457 菌株。因此，为了更好地将 B 重复序列的生物物理和结构研究结果与 体内研究联系起来，检查了来自菌株 1457 的 B 重复序列超结构域。菌株 RP62A 和 1457 的 B 重复序列之间的差异包括 B 重复序列的数量，这已被证明在组装成淀粉样蛋白原纤维中起关键作用，以及共有和变体 B 重复序列亚型的分布，它们在组装能力和热稳定性方面有所不同。使用分析超速离心对菌株 1457 中 Zn 诱导的完整 B 重复序列超结构域的组装进行了详细研究。RP62A （Brpt5.5） 的先前构建体在聚集前形成稳定的四聚体，而 1457 年的 Brpt6.5 在聚集成类似的淀粉样蛋白原纤维之前形成 ≈28 聚体量级的极大稳定物种。 我们的数据表明，两种组装途径都可能通过相同的二聚化和四聚化机制进行，并且都以淀粉样蛋白原纤维的形成结束。讨论了来自不同菌株和不同长度的 B 重复序列的组装行为，并考虑了生物学意义。