Allosteric regulation of a prokaryotic small Ras-like GTPase contributes to cell polarity oscillations in bacterial motility
Fig 5
MxMglB Ct-helix is required for MxMglB function in vivo.
(A) Expression of MxMglBΔCt leads to motility defects. Motility on 0.5% agar is shown after 48 hours of incubation at 32°C. Scale bar = 1 cm. (B) Reversal frequency of M. xanthus cells of ΔmglB mutant strain and cells expressing wild-type MxMglB (mglB+) or MxMglBΔCt (mglBΔCt+). The reversal frequencies were scored in absence (−) or presence (+) of 0.075% IAA, a condition known to activate the Frz system. For each strain and condition, the number of trajectories analyzed (n), the median (vertical line), and the mean (black dot) are reported for each box-and-whisker plot. (C) MxMglBΔCt shows a bipolar localization pattern. Representative fields of cells expressing MxMglBΔCt-nG and MxMglB-nG are shown in top and bottom images, respectively. The fractions of cells exhibiting bipolar (dark blue), unipolar (light blue), and diffuse (cyan) localization are depicted on the left for each of the field views, in which “n” represents the total number of cells analyzed. The fluorescence intensity profiles for each cell are compiled and shown in S4A Fig. (D) MxMglA shows a bipolar localization pattern in the presence of MxMglBΔCt. Representative fields of cells expressing MxMglA-YFP in mglBΔCt+ and mglB+ strains are shown in top and bottom images, respectively. The fractions of cells exhibiting bipolar, unipolar, and diffuse localization are depicted on the left for each of the field views, in which “n” represents the total number of cells analyzed. The fluorescence intensity profiles for each cell are compiled and shown in S4B Fig. (E) RomR shows a bipolar localization pattern in the presence of MxMglBΔCt. Representative fields of cells expressing RomR-GFP in mglBΔCt+ and mglB+ strains are shown in top and bottom images, respectively. The fractions of cells exhibiting bipolar, unipolar, and diffuse localization are depicted on the left for each of the field views, in which “n” represents the total number of cells analyzed. In the bottom panel (RomR-GFP, mglB+), dashed lines indicate bacterial contour. The fluorescence intensity profiles for each cell are compiled and shown in S4B Fig. The numerical data for all the figure panels have been provided in the respective sheets in S1 Data. Ct-helix, C-terminal helix; Frz, frizzy; IAA, isoamyl alcohol; MxMglA, M. xanthus MglA; MxMglB, M. xanthus MglB; MxMglBΔCt, MxMglB with Ct-helix truncated; nG, neonGreen; YPF, yellow fluorescent protein.