Crystallization of human complement component C3b in the presence of a staphylococcal complement-inhibitor protein (SCIN)
Crystallization of human complement component C3b in the presence of a staphylococcal complement-inhibitor protein (SCIN)
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DOI：
10.1107/s174430910901207x
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发表时间：
2009-05-01
影响因子：
0.9
通讯作者：
Geisbrecht, Brian V.
中科院分区：
文献类型：
--
作者：
Garcia, Brandon L.;Tzekou, Apostolia;Geisbrecht, Brian V.
金黄色葡萄球菌分泌许多小蛋白质，有效地减弱人类先天免疫反应。其中，葡萄球菌补体抑制蛋白（SCIN）破坏补体成分3（C3）转化酶的功能，所述补体成分3（C3）转化酶通过经典途径或旁路途径启动，从而防止细菌表面上补体应答的扩增。最近的研究表明，SCIN可能通过以等摩尔方式结合C3 b来影响C3转化酶的活性，C3 b本身是转化酶的一个不可或缺的非酶成分。为了更好地理解C3 b-SCIN相互作用的性质，使用悬滴气相扩散技术在重组形式的SCIN存在下使人C3 b结晶。这些晶体衍射同步加速器X射线到大约6埃的布拉格间距，并在原始的四元空间群（P4（1）2（1）2或P4（3）2（1）2;晶胞参数a = B = 128.03，c = 468.59埃）中生长。这些晶体的细胞含量分析与在不对称单元中存在两个1：1复合物或单个2：2组装体一致，这两者都对应于51.9%的溶剂含量。通过利用这些晶体，C3 b-SCIN结构的解决方案将进一步加深我们对该病原体的补体抑制和免疫逃避的理解。
Staphylococcus aureus secretes a number of small proteins that effectively attenuate the human innate immune response. Among these, the staphylococcal complement-inhibitor protein (SCIN) disrupts the function of the complement component 3 (C3) convertase that is initiated through either the classical or the alternative pathway and thereby prevents amplification of the complement response on the bacterial surface. Recent studies have shown that SCIN may affect the activities of the C3 convertase by binding in an equimolar fashion to C3b, which is itself an integral although non-enzymatic component of the convertase. In order to better understand the nature of the C3b-SCIN interaction, the hanging-drop vapor-diffusion technique was used to crystallize human C3b in the presence of a recombinant form of SCIN. These crystals diffracted synchrotron X-rays to approximately 6 angstrom Bragg spacing and grew in a primitive tetragonal space group (P4(1)2(1)2 or P4(3)2(1)2; unit-cell parameters a = b = 128.03, c = 468.59 angstrom). Cell-content analysis of these crystals was consistent with the presence of either two 1: 1 complexes or a single 2: 2 assembly in the asymmetric unit, both of which correspond to a solvent content of 51.9%. By making use of these crystals, solution of the C3b-SCIN structure should further our understanding of complement inhibition and immune evasion by this pathogen.