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

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 R egulatory L ight C hain 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 Brief Kapoor et al . report the crystal structure of Myxococcus xanthus MglC, a R oadblock L ight C hain 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. Highlights MglC 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.