Between reversals, MglA ·GTP and MglB localize to the leading and lagging pole, respectively, in this way defining the leading/lagging polarity axis.
Between reversals, MglA/GTP is restricted to the leading and MglB to the lagging pole defining the leading/lagging polarity axis.
As we directly showed that MglB has MglAGAP activity, MglB likely excludes MglA/GTP from the lagging pole between reversals by locally converting MglA/GTP to MglA/GDP.
For reversals, the Frz chemosensory system induces the relocation of MglA/GTP to the lagging pole causing an inversion of the leading/lagging polarity axis.
Second, after the two RomR-GFP clusters have attained equal intensities, the RomR cluster at the old lagging pole continues to decrease in intensity, whereas the intensity of the cluster at the old leading pole continues to increase.
It is also interesting to note that translocation of MglA+ and MglAG21V from the leading to the lagging pole occurs in a highly directed manner (cf. Figure 2B D) unlike that expected for freely diffusing molecules and on a timescale much slower than diffusion (Bulyha et al, 2009).
Moving cells containing YFP MglAG21V reversed in a highly regular manner approximately every 4 min. YFP MglAG21V formed a cluster that was continuously and regularly oscillating from the leading towards the lagging pole with a velocity of 1.3±0.2 μm min 1, each 'arrival' of the cluster at the lagging cell pole correlating with reversal.
The two separable activities of MglA, their differential dependency on Frz, and the localization patterns of the mutant MglA proteins suggest that Frz by further stimulating accumulation of MglA/GTP induces the release of MglA/GTP from the leading pole and the subsequent relocation towards the lagging pole.
In the frzlof mutant, the same localization pattern of YFP MglAG21V was observed as in the frz+ strain and with YFP MglAG21V forming a cluster that oscillated regularly between the poles with a 4 min half-period, each 'arrival' of the cluster at the lagging pole correlating with reversal.
The targeting factor(s) either switch from the old lagging pole to the new lagging pole or are unmasked at the new lagging pole and masked at the old lagging pole during a reversal.
RomR possibly stimulates polyelectrolyte secretion, and the pole-to-pole transfer of the large RomR cluster during a reversal possibly results in inactivation of the nozzles at the old lagging pole and activation of the nozzles at the new lagging pole.
