Abstract
Dynamic control of cell polarity is of critical importance for many aspects of cellular development and motility. In Myxococcus xanthus a three-protein module MglA, MglB and RomR, forms a polarity axis that can be rapidly inverted by the Frz chemosensory system to change the direction of movement. However, how Frz signalling provokes the polarity switch has remained unknown. Here, we show that Frz exerts spatial regulations at both cell poles. At the lagging cell pole, RomR and FrzX, a newly identified Frz regulator, form a two-component checkpoint that triggers the switch when MglA and FrzX-P concentrations are sufficiently high. At the leading cell pole, the FrzZ protein overcomes the slow unbinding of RomR to provoke fast reversals when Frz signalling is high. Mathematical modelling reveals that this architecture creates a spatiotemporal oscillator with highly tunable properties allowing a wide range of motility responses to internal and external signals.