PDF(Pubmed)
Abstract：
Bacterial adhesins are cell-surface proteins that anchor to the cell wall of the host. The first stage of infection involves the specific attachment to fibrinogen (Fg), a protein found in human blood. This attachment allows bacteria to colonize tissues causing diseases such as endocarditis. The study of this family of proteins is hence essential to develop new strategies to fight bacterial infections. In the case of the Gram-positive bacterium Staphylococcus aureus, there exists a class of adhesins known as microbial surface components recognizing adhesive matrix molecules (MSCRAMMs). Here, we focus on one of them, the clumping factor A (ClfA), which has been found to bind Fg through the dock-lock-latch mechanism. Interestingly, it has recently been discovered that MSCRAMM proteins employ a catch-bond to withstand forces exceeding 2 nN, making this type of interaction as mechanically strong as a covalent bond. However, it is not known whether this strength is an evolved feature characteristic of the bacterial protein or is typical only of the interaction with its partner. Here, we combine single-molecule force spectroscopy, biophysical binding assays, and molecular simulations to study the intrinsic mechanical strength of ClfA. We find that despite the extremely high forces required to break its interactions with Fg, ClfA is not by itself particularly strong. Integrating the results from both theory and experiments we dissect contributions to the mechanical stability of this protein.
摘要：
细菌粘附素是锚定在宿主细胞壁上的细胞表面蛋白。感染的第一阶段涉及对纤维蛋白原（Fg）的特异性附着，在人体血液中发现的蛋白质。这种附着允许细菌定植于引起诸如心内膜炎的疾病的组织。因此，对该蛋白质家族的研究对于开发对抗细菌感染的新策略至关重要。在革兰氏阳性细菌金黄色葡萄球菌的情况下，存在一类被称为识别粘合剂基质分子(MSCRAMMs)的微生物表面组分的粘附素。这里,我们专注于其中一个，结块因子A(ClfA)，已发现通过坞-锁-闩锁机制绑定Fg。有趣的是,最近已经发现MSCRAMM蛋白使用捕获键来承受超过2nN的力，使这种相互作用在机械上像共价键一样强大。然而,不知道这种强度是否是细菌蛋白质的进化特征特征，或者仅是与其伴侣相互作用的典型特征。这里,我们结合了单分子力谱，生物物理结合测定，和分子模拟研究ClfA的固有机械强度。我们发现，尽管需要极高的力量来打破它与Fg的相互作用，ClfA本身不是特别强。综合理论和实验的结果，我们剖析了对该蛋白质机械稳定性的贡献。
