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Analyzing the Function of Small GTPases by Microinjection of Plasmids into Polarized Epithelial Cells
Published on: May 31, 2011
Cell polarity control by an unconventional G-protein complex in bacteria
Céline Dinet1,2,3, Corinne Sebban-Kreuzer4, Deborah Byrne-Kodjabachian5
1Laboratoire de Chimie bactérienne (LCB), Institut de Microbiologie de la Méditerranée (IMM), Aix-Marseille Université, CNRS (UMR7283), Turing Centre for Living Systems (Centuri), Marseille, France.
Nature Communications
|June 15, 2026
Summary
Researchers clarified the roles of MglA, MglB, and RomRX in Myxococcus xanthus motility. RomRX binds MglA-GTP, and MglB acts as both GAP and GEF, with RomR mediating interactions to control polarity.
Area of Science:
- Microbiology
- Cell Biology
- Biochemistry
Background:
- Cell polarity and motility in Myxococcus xanthus are crucial for its predatory behavior.
- The small GTPase MglA and its regulators MglB and RomRX are implicated in this process, but their exact functions are not fully understood.
Purpose of the Study:
- To elucidate the precise molecular mechanisms by which MglA, MglB, and RomRX regulate cell polarity and motility in M. xanthus.
- To determine the guanine nucleotide exchange factor (GEF) and GTPase-activating protein (GAP) activities of RomRX and MglB, respectively.
Main Methods:
- Fluorescence anisotropy measurements using fluorescent nucleotides to study protein-nucleotide interactions.
- Enzymatic modeling to analyze the GAP and GEF activities of MglB.
- Biomimetic oil-emulsion droplet assays in cell-sized systems to visualize protein partitioning in vivo.
- Development of a minimal mathematical model to simulate the dynamic interactions.
Main Results:
- RomRX was identified as an effector that binds MglA-GTP, not a GEF.
- MglB demonstrated both GAP and GEF activities, dependent on MglA-GDP concentration.
- RomR (a component of RomRX) sequesters MglB, dissociating the MglA-MglB complex and enabling GAP activity.
- In vivo protein partitioning was observed in cell-sized emulsion droplets, consistent with low-affinity interactions.
Conclusions:
- The study redefines the roles of RomRX and MglB in the MglA regulatory network.
- Dynamic, context-dependent interactions between MglA, MglB, and RomRX are essential for establishing an invertible polarity axis in M. xanthus.
- These findings provide a comprehensive model for polarity regulation in this bacterium.
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