Structural characterization ofMyxococcus xanthusMglC, a component of polarity control system, and its interactions with MglB

Abstract

Myxococcus xanthus displays two types of motilities i.e. Social (S) and Adventurous (A). The pole-to-pole reversals of these motility regulator proteins is the key to this process. Here, we determined ~1.85 Å resolution crystal structure of MglC, which revealed that despite sharing <9% sequence identity, both MglB and MglC adopt Regulatory Light Chain 7 (RLC7) family fold. Interestingly, MglC is structurally unique compared to the other known RLC7 family proteins having ~30°-40° shift in the orientation of functionally important α2 helix. Using isothermal titration calorimetry and gel filtration chromatography, we show that MglC binds MglB in 2:4 stoichiometry with submicromolar range dissociation constant. Using combination of small angle X-ray scattering and molecular docking studies, we show that MglBC complex is formed by MglC homodimer sandwiched between two homodimers of MglB.In BriefKapoor et al. report the crystal structure of Myxococcus xanthus MglC, a Roadblock Light Chain 7 (RLC7) family protein, involved in polarity reversal. The structure reveals a distinct orientation of α2 helix compared to other RLC7 proteins. They also demonstrate that MglC binds a GTPase activating protein, MglB, with submicromolar range dissociation constant.HighlightsMglC adopts RLC7 fold and has distinct structural features.MglC interacts MglB to form a stable complex having submicromolar range dissociation constant.MglC homodimer is sandwiched between two MglB homodimers to form a 2:4 stoichiometric complex.