Structural and functional study of MCP2201 from CNB-1
作者单位：National Laboratory of Biomacromolecules Institute of Biophysics Chinese Academy of Sciences
会议名称：《第五届中国结构生物学学术讨论会》
会议日期：2016年
学科分类：0710[理学-生物学] 071010[理学-生物化学与分子生物学] 081704[工学-应用化学] 07[理学] 08[工学] 0817[工学-化学工程与技术]
摘 要：Chemotaxis is an important physiological response to chemical compounds and enables bacteria to be more competitive for nutrition and avoidance of harsh conditions. The study of chemoreceptors, also known as methyl-accepting chemotaxis proteins（MCPs）, provides us the chance of understanding the chemotaxis mechanism and the transmembrane signaling mechanism. A piston model for the chemoreceptor transmembrane signaling has been proposed for at least ten years and not yet been demonstrated by the structures of ligand-free and-bound states. Here we reported the crystal structures of attractant-free and-bound ligand-binding-domain（LBD2201） of MCP2201, a recently identified chemoreceptor from Comamonas testosteroni CNB-1. The comparison of the protomer structure in attractant-free and-bound forms indicated a loop-tohelix transition in the N-terminus of helix α2 upon attractant binding, which exactly illustrated the structural basis of the piston model for the chemoreceptor transmembrane signaling. Interestingly, the attractant-free and-bound LBD2201 exist as a dimer used to be observed for other chemoreceptors and a trimer never observed previously, respectively, implying that an associationdisassociation model should be involved in the transmembrane signaling of chemoreceptors. Mutation based crosslinking experiments on living bacteria stimulated by the attractant captured expected trimer, implying which exists exactly in vivo. Motility plate assays showed mutations that are designed to disrupt trimer interface or interactions between attractant molecule and ligand binding cavity lost their chemotaxis activity toward the attractant. This suggested chemotaxis activation of MCP2201 depends on a dimer-to-trimer transition upon the attractant binding. In a summary, our study provided a new insight into the activating mechanism of MCPs and the transmembrane signaling.