Ministry of Education Key Laboratory for Membraneless Organelles & Cellular Dynamics, Hefei National Laboratory for Physical Sciences at the Microscale, School of Life Sciences, Division of Life Sciences and Medicine, University of Science and Technology of China, 230027 Hefei, P.R. China.
Hefei National Laboratory for Physical Sciences at the Microscale, School of Life Sciences, Division of Life Sciences and Medicine, University of Science and Technology of China, 230027 Hefei, P.R. China.
Proc Natl Acad Sci U S A. 2020 Dec 1;117(48):30433-30440. doi: 10.1073/pnas.1912080117. Epub 2020 Nov 16.
Two-component systems (TCS), which typically consist of a membrane-embedded histidine kinase and a cytoplasmic response regulator, are the dominant signaling proteins for transduction of environmental stimuli into cellular response pathways in prokaryotic cells. HptRSA is a recently identified TCS consisting of the G6P-associated sensor protein (HptA), transmembrane histidine kinase (HptS), and cytoplasmic effector (HptR). HptRSA mediates glucose-6-phosphate (G6P) uptake to support growth and multiplication within various host cells. How the mechanism by which HptRSA perceives G6P and triggers a downstream response has remained elusive. Here, we solved the HptA structures in apo and G6P-bound states. G6P binding in the cleft between two HptA domains caused a conformational closing movement. The solved structures of HptA in complex with the periplasmic domain of HptS showed that HptA interacts with HptS through both constitutive and switchable interfaces. The G6P-free form of HptA binds to the membrane-distal side of the HptS periplasmic domain (HptSp), resulting in a parallel conformation of the HptSp protomer pair. However, once HptA associates with G6P, its intramolecular domain closure switches the HptA-HptSp contact region into the membrane-proximal domain, which causes rotation and closure of the C termini of each HptSp protomer. Through biochemical and growth assays of HptA and HptS mutant variants, we proposed a distinct mechanism of interface switch-mediated signaling transduction. Our results provide mechanistic insights into bacterial nutrient sensing and expand our understanding of the activation modes by which TCS communicates external signals.
双组分系统（TCS）通常由膜嵌入组氨酸激酶和细胞质响应调节剂组成，是原核细胞中环境刺激转导为细胞反应途径的主要信号蛋白。HptRSA 是一种新鉴定的 TCS，由 G6P 相关传感器蛋白（HptA）、跨膜组氨酸激酶（HptS）和细胞质效应物（HptR）组成。HptRSA 介导葡萄糖-6-磷酸（G6P）摄取，以支持各种宿主细胞中的 生长和增殖。HptRSA 感知 G6P 并触发下游反应的机制仍然难以捉摸。在这里，我们解决了 HptA 在apo 和 G6P 结合状态下的结构。G6P 在两个 HptA 结构域之间的裂隙中的结合引起构象关闭运动。与 HptS 周质域复合物的 HptA 结构表明，HptA 通过组成型和可切换接口与 HptS 相互作用。无 G6P 的 HptA 形式与 HptS 的周质域（HptSp）的膜远端侧结合，导致 HptSp 单体对的平行构象。然而，一旦 HptA 与 G6P 结合，其分子内结构域关闭将 HptA-HptSp 接触区域切换到膜近端结构域，从而导致每个 HptSp 单体的 C 末端旋转和关闭。通过 HptA 和 HptS 突变变体的生化和生长测定，我们提出了一种独特的界面开关介导信号转导机制。我们的结果为细菌营养感应提供了机制见解，并扩展了我们对 TCS 传达外部信号的激活模式的理解。
