The crystal structure of the phytopathogenic bacterial sensor PcrK reveals different cytokinin recognition mechanism from the plant sensor AHK4
The crystal structure of the phytopathogenic bacterial sensor PcrK reveals different cytokinin recognition mechanism from the plant sensor AHK4
复制标题
植物病原细菌传感器PcrK的晶体结构揭示了与植物传感器AHK4不同的细胞分裂素识别机制
DOI：
10.1016/j.jsb.2019.08.001
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发表时间：
2019-10-01
影响因子：
3
通讯作者：
Ming, Zhenhua
中科院分区：
文献类型：
--
作者：
Chen, Peng;Jiao, Xi;Ming, Zhenhua
植物细胞分裂素（CK）是许多细胞活动的必需物质，在细菌与植物的相互作用中起着重要作用。CK的感知由一类双组分调节系统的组氨酸激酶传感器中的CHASE结构域执行。尽管在理解拟南芥中传感器AHK4感知CK的结构基础方面取得了进展，但其他传感器结合CK的分子机制尚不清楚。在这里，我们报告的晶体结构的CHASE结构域中的组氨酸激酶PcrK的细菌性植物病原体野油菜黄单胞菌pathovar野油菜，这感觉植物CK，确定在2.55埃分辨率。结构表明，PcrK具有AHK4样的整体拓扑结构，并组装成同源二聚体。引人注目的是，详细的结构分析揭示了PcrK配体结合口袋的两个独特特征：口袋的大小限制于CK结合，并且PcrK应用带正电荷的精氨酸而不是带负电荷的天冬氨酸来识别配体。我们提出了一个模型来解释如何PcrK容纳CK大小的化合物通过构象变化，提供了一个潜在的机制框架，了解配体识别的PcrK。
Plant cytokinins (CKs) are essential for many central cellular processes and play important roles in the interaction between bacteria and plants. Perception of CK is executed by the CHASE domain in the histidine kinase sensors of a class of two-component regulatory systems. Despite advances in understanding the structural basis for CK perception by the sensor AHK4 in Arabidopsis, the molecular mechanism of CK binding by other sensors is unclear. Here, we report the crystal structure of the CHASE domain in the histidine kinase PcrK of the bacterial plant pathogen Xanthomonas campestris pathovar campestris, which senses plant CK, determined at 2.55 angstrom resolution. The structure reveals that the PcrK has an AHK4-like overall topology and assembles into a homodimer. Strikingly, detailed structural analysis unveils two unique features of the PcrK ligand binding pocket: the size of the pocket is restricted for CK binding, and the PcrK applies a positively charged arginine but not a negatively charged aspartate to recognize the ligand. We propose a model to explain how the PcrK accommodates CK-sized compounds through conformational changes, providing a potential mechanistic framework for understanding ligand recognition by the PcrK.