a bacterial ras-like small gtp-binding protein and its cognate gap establish a dynamic spatial polarity axis to control directed motility细菌ras-like小gtp-binding蛋白质及其同源差距建立动态空间极性轴控制定向的能动性.pdfVIP

A Bacterial Ras-Like Small GTP-Binding Protein and Its Cognate GAP Establish a Dynamic Spatial Polarity Axis to Control Directed Motility 1,2 3 1 ˆ 1 Yong Zhang , Michel Franco , Adrien Ducret , Tam Mignot * ´ ´ ´ ´ 1 Institut de Microbiologie de la Mediterranee–Universite Aix-Marseille-Laboratoire de Chimie Bacterienne, Marseille, France, 2 State Key Laboratory of Microbial ´ ´ Technology, College of Life Science, Shandong University, Jinan, China, 3 Institut de Pharmacologie Moleculaire et Cellulaire–Universite de Nice-Sophia Antipolis, Valbonne, France Abstract Regulated cell polarity is central to many cellular processes. We investigated the mechanisms that govern the rapid switching of cell polarity (reversals) during motility of the bacterium Myxococcus xanthus. Cellular reversals are mediated by pole-to-pole oscillations of motility proteins and the frequency of the oscillations is under the control of the Frz chemosensory system. However, the molecular mechanism that creates dynamic polarity remained to be characterized. In this work, we establish that polarization is regulated by the GTP cycle of a Ras-like GTPase, MglA. We initially sought an MglA regulator and purified a protein, MglB, which was found to activate GTP hydrolysis by MglA. Using live fluorescence microscopy, we show that MglA and MglB localize at opposite poles and oscillate oppositely when cells reverse. In absence of MglB, MglA-YFP accumulates at the lagging cell end, leading to a strikingly