Yarawsky Alexander E, Herr Andrew B
Division of Immunobiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio.
Division of Immunobiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio; Division of Infectious Diseases, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio; Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, Ohio.
Biophys J. 2025 Jan 21;124(2):363-378. doi: 10.1016/j.bpj.2024.12.011. Epub 2024 Dec 11.
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.
聚集相关蛋白（Aap）是表皮葡萄球菌装置相关感染的主要决定因素。B重复超结构域负责细胞间粘附，导致此类感染中生物膜的形成。最近有研究表明，锌诱导的B重复组装导致功能性淀粉样纤维的形成，为生物膜提供强度和稳定性。对表皮葡萄球菌RP62A菌株的Aap B重复序列进行的严格生物物理研究表明，在聚集形成淀粉样纤维之前，锌诱导其组装成稳定、可逆的二聚体和四聚体。对于包括RP62A在内的许多表皮葡萄球菌菌株，基因操作并不容易；相反，许多基因研究使用的是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，对1457菌株的B重复超结构域进行了研究。RP62A菌株和1457菌株的B重复序列之间的差异包括B重复序列的数量，已证明其在组装成淀粉样纤维中起关键作用，以及共有和变异B重复亚型的分布，它们在组装能力和热稳定性方面存在差异。使用分析超速离心法对1457菌株的完整B重复超结构域的锌诱导组装进行了详细研究。虽然之前来自RP62A的构建体（Brpt5.5）在聚集之前形成了稳定的四聚体，但来自1457的Brpt6.5在聚集形成类似的淀粉样纤维之前，形成了约28聚体大小的极其大的稳定物种。我们的数据表明，两种组装途径可能通过相同的二聚化和四聚化机制进行，并且都以形成淀粉样纤维告终。本文讨论了不同菌株和不同长度的B重复序列的组装行为，并考虑了其生物学意义。
