期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2015
卷号：112
期号：2
页码：E186-E193
DOI：10.1073/pnas.1421073112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceThe bacterium Myxococcus xanthus moves on surfaces by directed gliding motility. MglA, a Ras family GTPase, regulates cell polarity in M. xanthus; However, little is known about how MglA establishes cell polarity during gliding, because gliding motors move simultaneously in opposite directions. We found that MglA interacts with the gliding motors directly and is localized in a decreasing intracellular gradient. Furthermore, the motors tend to reverse their moving direction at locations where the activity of MglA is high. Our data suggest that biased reversals along the MglA gradient make the motors moving toward the lagging cell poles less likely to reverse, generating stronger forward propulsion. Thus, bacterial cells, like eukaryotic cells, can use Ras homolog localization to establish cellular polarity. Gliding motility in Myxococcus xanthus is powered by flagella stator homologs that move in helical trajectories using proton motive force. The Frz chemosensory pathway regulates the cell polarity axis through MglA, a Ras family GTPase; however, little is known about how MglA establishes the polarity of gliding, because the gliding motors move simultaneously in opposite directions. Here we examined the localization and dynamics of MglA and gliding motors in high spatial and time resolution. We determined that MglA localizes not only at the cell poles, but also along the cell bodies, forming a decreasing concentration gradient toward the lagging cell pole. MglA directly interacts with the motor protein AglR, and the spatial distribution of AglR reversals is positively correlated with the MglA gradient. Thus, the motors moving toward lagging cell poles are less likely to reverse, generating stronger forward propulsion. MglB, the GTPase-activating protein of MglA, regulates motor reversal by maintaining the MglA gradient. Our results suggest a mechanism whereby bacteria use Ras family proteins to modulate cellular polarity.
关键词：gliding motility ; cell polarity ; single molecule ; protein dynamics ; sptPALM
