Hefei National Laboratory for Physical Sciences at Microscale, School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, PR China.
Sci Rep. 2013;3:1079. doi: 10.1038/srep01079. Epub 2013 Jan 16.
Streptococcus pneumoniae is a pathogen causing acute respiratory infection, otitis media and some other severe diseases in human. In this study, the solution structure of a bacterial immunoglobulin-like (Big) domain from a putative S. pneumoniae surface protein SP0498 was determined by NMR spectroscopy. SP0498 Big domain adopts an eight-β-strand barrel-like fold, which is different in some aspects from the two-sheet sandwich-like fold of the canonical Ig-like domains. Intriguingly, we identified that the SP0498 Big domain was a Ca(2+) binding domain. The structure of the Big domain is different from those of the well known Ca(2+) binding domains, therefore revealing a novel Ca(2+)-binding module. Furthermore, we identified the critical residues responsible for the binding to Ca(2+). We are the first to report the interactions between the Big domain and Ca(2+) in terms of structure, suggesting an important role of the Big domain in many essential calcium-dependent cellular processes such as pathogenesis.
肺炎链球菌是一种病原体，可导致人类急性呼吸道感染、中耳炎和其他一些严重疾病。在这项研究中，通过 NMR 光谱法确定了一种假定来自肺炎链球菌表面蛋白 SP0498 的细菌免疫球蛋白样 (Big) 结构域的溶液结构。SP0498 Big 结构域采用八-β-链桶状折叠，在某些方面与典型 Ig 样结构域的两片夹心折叠不同。有趣的是，我们鉴定出 SP0498 Big 结构域是一个 Ca(2+)结合结构域。该结构域的结构与众所周知的 Ca(2+)结合结构域不同，因此揭示了一种新型 Ca(2+)结合模块。此外，我们鉴定出与 Ca(2+)结合相关的关键残基。我们首次从结构上报告了 Big 结构域与 Ca(2+)之间的相互作用，表明 Big 结构域在许多重要的钙依赖性细胞过程（如发病机制）中发挥重要作用。
