title: Solution structure of the Big domain from Streptococcus pneumoniae reveals a novel Ca2+-binding module.
abstract: 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.
authors: Hefei National Laboratory for Physical Sciences at Microscale, School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, PR China.
authors: Tao
authors: T
authors: Wang
authors: Jiahai
authors: J
authors: Zhang
authors: Xuecheng
authors: X
authors: Zhang
authors: Chao
authors: C
authors: Xu
authors: Xiaoming
authors: X
authors: Tu
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002942:Circular Dichroism; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D013296:Streptococcus pneumoniae / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D002118:Calcium