结核分枝杆菌伴侣蛋白触发因子与核糖体蛋白 S7 复合物的结构研究

Structural insights into the complex of trigger factor chaperone and ribosomal protein S7 from Mycobacterium tuberculosis.

机构信息

State Key Laboratory of Genetic Engineering, School of Life Science, Collaborative Innovation Center of Genetics and Development, Fudan University, Shanghai, 200438, China.

出版信息

Biochem Biophys Res Commun. 2019 May 14;512(4):838-844. doi: 10.1016/j.bbrc.2019.03.166. Epub 2019 Mar 28.

DOI:10.1016/j.bbrc.2019.03.166

PMID:30928093

Abstract

Tuberculosis, caused by Mycobacterium tuberculosis (Mtb), has threaten human health for thousands years. The chaperone trigger factor (TF) of Mtb (mtbTF), a ribosome-associated molecule, plays important roles in co-translational nascent chain folding and post-translational protein assembly. However, due to lack of structural information, the dynamic regulatory mechanism of mtbTF remains barely investigated. Herein we report the structural basis of the complex of TF and ribosomal protein S7 (mtbS7) from Mtb. The mtbTF-mtbS7 complex was obtained with high purity and homogeneity in vitro. MtbTF bound with mtbS7 in a K value of 1.433 μM, and formed a complex with mtbS7 at 1:2 M ratios as shown by isothermal titration calorimetry. In addition, the crystal structure of mtbS7 was solved to a resolution at 1.8 Å, which was composed of six α-helices and two β-strands. Moreover, the molecular envelopes of mtbTF and mtbTF-mtbS7 complex were built and consisted with these homologous structures by small-angle X-ray scattering method. Our current findings might provide structural basis for understanding the molecular mechanism of TF in protein folding and the regulation of ribosomal assembly in Mtb.

摘要

结核病是由结核分枝杆菌（Mycobacterium tuberculosis，Mtb）引起的，它已经威胁人类健康数千年了。结核分枝杆菌伴侣蛋白触发因子（chaperone trigger factor，TF）（mtbTF）是一种与核糖体相关的分子，在共翻译新生链折叠和翻译后蛋白组装中发挥重要作用。然而，由于缺乏结构信息，mtbTF 的动态调控机制仍鲜有研究。在此，我们报道了结核分枝杆菌核糖体蛋白 S7（ribosomal protein S7，mtbS7）与 TF 复合物的结构基础。体外实验获得了高纯度和均一性的 mtbTF-mtbS7 复合物。等温滴定量热法（isothermal titration calorimetry，ITC）结果表明，mtbTF 与 mtbS7 的结合常数（Kd）为 1.433 μM，以 1:2 M 的比例形成复合物。此外，我们解析了 mtbS7 的晶体结构，分辨率达到 1.8 Å，其由六个α螺旋和两个β链组成。此外，通过小角 X 射线散射（small-angle X-ray scattering，SAXS）方法构建了 mtbTF 和 mtbTF-mtbS7 复合物的分子包络，这些结构与同源结构一致。我们的研究结果可能为理解 TF 在蛋白质折叠和 Mtb 核糖体组装调控中的分子机制提供结构基础。