Nagarajan Revathi, Hendrickx Antoni P A, Ponnuraj Karthe
Centre of Advanced Study in Crystallography and Biophysics, University of Madras, Chennai, India.
Department of Medical Microbiology, University Medical Center Utrecht, The Netherlands.
FEBS J. 2016 Aug;283(16):3039-55. doi: 10.1111/febs.13792. Epub 2016 Jul 14.
Antimicrobial-resistant and hospital-adapted Enterococcus faecium represents a clinical problem in immunocompromised patients in hospitals worldwide. Understanding the molecular pathogenesis of E. faecium infections may provide novel therapies to treat or prevent infections. A potential target for novel treatment therapies is the serine-glutamate repeat containing protein A (SgrA), which is a cell wall-anchored LPxTG surface protein implicated in binding to fibrinogen and nidogen. Here, we report the X-ray crystal structure of the N-terminal ligand-binding domain of SgrA (rSgrA28-153 ) to a resolution of 1.79 Å. The structure revealed a new protein fold with significant differences from previously characterized DEv-IgG- and inv-IgG-like folds of adhesive proteins known as microbial surface components recognizing adhesive matrix molecules. The structure contains a Lys-Asn-Glu triad with the potential to form a Lys-Asn isopeptide bond. However, even in the absence of a stabilizing intramolecular isopeptide bond, rSgrA28-153 exhibits remarkable properties like resistance to proteases and high thermal stability. The interaction of rSgrA28-153 with fibrinogen, nidogen, laminin, and abiotic surfaces has been characterized and rSgrA28-153 binds to these molecules with high affinity. rSgrA28-153 also binds to the beta chain of fibrinogen and with high affinity and specificity. Strikingly, the presence of 29 surface-exposed hydrophobic amino acid residues likely play an important role in the selectivity of rSgrA28-153 to bind to different abiotic surfaces. The results obtained from this study have opened new avenues to explore and understand the role of this unique surface adhesin in the pathogenesis of catheter-related infections.
The coordinates and structure factors for rSgrA28-153 have been deposited with the accession code 5FCE.
耐抗菌且适应医院环境的粪肠球菌是全球医院中免疫功能低下患者面临的一个临床问题。了解粪肠球菌感染的分子发病机制可能会提供治疗或预防感染的新疗法。新型治疗方法的一个潜在靶点是含丝氨酸 - 谷氨酸重复序列的蛋白A（SgrA），它是一种细胞壁锚定的LPxTG表面蛋白，与纤维蛋白原和巢蛋白的结合有关。在此，我们报道了SgrA的N端配体结合结构域（rSgrA28 - 153）的X射线晶体结构，分辨率为1.79 Å。该结构揭示了一种新的蛋白质折叠方式，与先前表征的被称为微生物表面成分识别黏附基质分子的黏附蛋白的DEv - IgG和inv - IgG样折叠有显著差异。该结构包含一个具有形成Lys - Asn异肽键潜力的Lys - Asn - Glu三联体。然而，即使在没有稳定的分子内异肽键的情况下，rSgrA28 - 153仍表现出显著特性，如对蛋白酶的抗性和高热稳定性。已对rSgrA28 - 153与纤维蛋白原、巢蛋白、层粘连蛋白和非生物表面的相互作用进行了表征，并且rSgrA28 - 153以高亲和力结合这些分子。rSgrA28 - 153还以高亲和力和特异性结合纤维蛋白原的β链。引人注目的是，29个表面暴露的疏水氨基酸残基的存在可能在rSgrA28 - 153与不同非生物表面结合的选择性中起重要作用。本研究获得的结果为探索和理解这种独特的表面黏附素在导管相关感染发病机制中的作用开辟了新途径。
rSgrA28 - 153的坐标和结构因子已以登录代码5FCE存入。
