Structural studies of the periplasmic portion of the diguanylate cyclase CdgH from Vibrio cholerae.
Structural studies of the periplasmic portion of the diguanylate cyclase CdgH from Vibrio cholerae.
复制标题
霍乱弧菌二鸟苷酸环化酶 CdgH 周质部分的结构研究
DOI：
10.1038/s41598-017-01989-6
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发表时间：
2017-05-12
影响因子：
4.6
通讯作者：
Xie W
中科院分区：
文献类型：
--
作者：
Xu M;Wang YZ;Yang XA;Jiang T;Xie W
环二鸟苷酸单磷酸（c-di-GMP）是参与细菌信号转导的第二信使，由通常含有高度可变的周质信号识别结构域的二鸟苷酸环化酶（DGCs）产生。CdgH是一种DGC酶，调节霍乱弧菌中与皱纹相关的表型。CdgH具有两个N-末端串联的周质底物结合（PBPb）结构域用于其信号识别;然而，串联PBPb结构域的作用仍不清楚。在这里，我们报道了CdgH的周质部分的晶体结构，这表明两个串联PBPb域由典型的叶间配体结合结构组成。出乎意料的是，PBPb-I结构域结合显然已经从E.而PBPb-II结构域处于无配体的开放状态。与其他氨基酸结合蛋白的结构比较表明，尽管类似的配体结合口袋，PBPb-I结构域具有两个配体结合残基（E122和Y148）不保守的同系物，并参与亲水和疏水相互作用与L-精氨酸。等温滴定量热法表明PBPb-I主要是L-精氨酸/L-赖氨酸/L-鸟氨酸结合结构域，而PBPb-II结构域表现出对L-谷氨酰胺和L-组氨酸的偏好。值得注意的是，我们发现CdgH的周质部分在溶液中形成稳定的二聚体，并且L-精氨酸结合会引起二聚体的构象变化。
Cyclic diguanylate monophosphate (c-di-GMP) is a second messenger involved in bacterial signal transduction and produced by diguanylate cyclases (DGCs) generally containing highly variable periplasmic signal-recognition domains. CdgH is a DGC enzyme that regulates rugosity associated phenotypes in Vibrio cholerae. CdgH has two N-terminal tandem periplasmic substrate-binding (PBPb) domains for its signal recognition; however, the role of the tandem PBPb domains remains unclear. Here, we reported the crystal structure of the periplasmic portion of CdgH, which indicated that both tandem PBPb domains consist of typical interlobe ligand-binding architecture. Unexpectedly, the PBPb-I domain binds an L-arginine which apparently has been co-purified from the E. coli expression system, whereas the PBPb-II domain is in an unliganded open state. Structural comparison with other amino acid-binding proteins indicated that despite similar ligand-binding pockets, the PBPb-I domain possesses two ligand-binding residues (E122 and Y148) not conserved in homologs and involved in hydrophilic and hydrophobic interactions with L-arginine. Isothermal titration calorimetry indicated that the PBPb-I is primarily an L-arginine/L-lysine/L-ornithine-binding domain, whereas the PBPb-II domain exhibits a preference for L-glutamine and L-histidine. Remarkably, we found that the periplasmic portion of CdgH forms a stable dimer in solution and L-arginine binding would cause conformational changes of the dimer.