Preliminary X-ray diffraction analysis of CfaA, a molecular chaperone essential for the assembly of CFA/I fimbriae of human enterotoxigenic Escherichia coli.
Preliminary X-ray diffraction analysis of CfaA, a molecular chaperone essential for the assembly of CFA/I fimbriae of human enterotoxigenic Escherichia coli.
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CfaA 的初步 X 射线衍射分析，CfaA 是人产肠毒素大肠杆菌 CFA/I 菌毛组装所必需的分子伴侣。
DOI：
10.1107/s2053230x13033967
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发表时间：
2014
期刊：
影响因子：
--
通讯作者：
Xia,Di
中科院分区：
文献类型：
--
作者：
Bao,Rui;Esser,Lothar;Poole,Steven;McVeigh,Annette;Chen,YuXing;Savarino,StephenJ;Xia,Di
对革兰氏阴性菌中菌毛生物组装的理解主要源于对尿路致病性大肠杆菌菌毛和 1 型菌毛的研究，它们是由经典伴侣-引导途径 (CUP) 介导的。然而，CFA/I 菌毛是产肠毒素大肠杆菌 (ETEC) 的 5 类菌毛和肠道定植因子，建议通过替代伴侣途径 (ACP) 进行组装。 CUP 和 ACP 菌毛生物组装途径都需要周质伴侣的功能，但它们相应的蛋白质在一级序列中的相似性非常低。在这里，报道了通过悬滴蒸气扩散法 CFA/I 周质伴侣 CfaA 的结晶。 X 射线衍射数据集是从天然 CfaA 晶体收集到的，分辨率为 2 Å，铅和铂衍生物的分辨率分别为 1.8 和 2.8 Å。这些晶体表现出C2空间群的对称性，晶胞参数a = 103.6，b = 28.68，c = 90.60 Å，β = 119.7°。使用铂和铅衍生物的数据，通过反常散射实验的多次同晶置换得出初始相。这产生了一个可解释的电子密度图，显示了不对称单元中的一个 CfaA 分子。重原子衍生物的异常信号有助于序列分配。 CfaA 原子模型的细化正在进行中，预计将进一步了解参与分子伴侣介导的生物组装的分子伴侣大家族的三级结构的基本方面和允许的变化。
Understanding of pilus bioassembly in Gram-negative bacteria stems mainly from studies of P pili and type 1 fimbriae of uropathogenic Escherichia coli, which are mediated by the classic chaperone–usher pathway (CUP). However, CFA/I fimbriae, a class 5 fimbria and intestinal colonization factor for enterotoxigenic E. coli (ETEC), are proposed to assemble via the alternate chaperone pathway (ACP). Both CUP and ACP fimbrial bioassembly pathways require the function of a periplasmic chaperone, but their corresponding proteins share very low similarity in primary sequence. Here, the crystallization of the CFA/I periplasmic chaperone CfaA by the hanging-drop vapor-diffusion method is reported. X-ray diffraction data sets were collected from a native CfaA crystal to 2 Å resolution and to 1.8 and 2.8 Å resolution, respectively, from a lead and a platinum derivative. These crystals displayed the symmetry of space group C2, with unit-cell parameters a = 103.6, b = 28.68, c = 90.60 Å, β = 119.7°. Initial phases were derived from multiple isomorphous replacement with anomalous scattering experiments using the data from the platinum and lead derivatives. This resulted in an interpretable electron-density map showing one CfaA molecule in an asymmetric unit. Sequence assignments were aided by anomalous signals from the heavy-atom derivatives. Refinement of the atomic model of CfaA is ongoing, which is expected to further understanding of the essential aspects and allowable variations in tertiary structure of the greater family of chaperones involved in chaperone–usher mediated bioassembly.