Mechanism of GTPase activation of a prokaryotic small Ras-like GTPase MglA by an asymmetrically interacting MglB dimer

Abstract

Cell polarity oscillations in Myxococcus xanthus motility are driven by a prokaryotic 23 small Ras-like GTPase, MglA, which switches from one cell pole to the other in 24 response to extracellular signals. MglA dynamics is regulated by MglB, which 25 functions both as a GAP (GTPase activating protein) and a GEF (guanine nucleotide 26 exchange factor) for MglA. With an aim to dissect the role of asymmetry in the dual 27 GAP and GEF activities of MglB, we generated a functional MglAB complex by co28 expressing MglB with a linked construct of MglA and MglB. This strategy enabled us 29 to generate mutations of individual MglB protomers (MglB1 linked to MglA or MglB2) 30 and delineate their role in GEF and GAP activities.