Cell polarity control by an unconventional G-protein complex in bacteria
Abstract
In Myxococcus xanthus, a predatory soil bacterium, cell polarity and motility are regulated by MglA (a small GTPase) and its regulators, MglB (a potential GAP) and RomRX (a previously proposed GEF), but their precise roles remain unclear. Using fluorescent nucleotides suitable for fluorescence anisotropy measurements, we show that RomRX does not function as a GEF but instead acts as an effector binding MglA GTP . We further find, using an enzymatic model, that MglB exhibits both GAP and GEF properties depending on the local MglA GDP concentration. Additionally, RomRX, specifically RomR, effectively dissociates the MglA-MglB complex by sequestering MglB. This low-affinity interaction permits GAP activity while still partitioning the proteins in vivo, as shown by a biomimetic oil-emulsion droplet assay in a cell-sized system. A minimal mathematical model incorporating these interactions and previous findings recapitulates how dynamic interactions between these three players form an invertible polarity axis in the M. xanthus cell.
Cell polarity, the asymmetric organization of cellular components, is a fundamental characteristic of many living organisms. It is essential for effective cell motility and a myriad of other directional functions, such as epithelial transport, neuronal signaling, and body axis specification in embryos 1,2 . A polarized cell establishes a distinct axis with a specific front, known as the polarity site, enabling it to maintain functionally distinct domains. This ability relies on intricate interactions between various protein complexes, including small GTPases, polarity proteins, and cytoskeletal components, that regulate multiple signaling pathways. In most eukaryotic cells, small GTPases of the Ras superfamily act as molecular switches in many signaling pathways and play a central role in cell polarization processes. For example, the Rho-family GTPases, including Cdc42 (one of the most highly conserved GTPases) and its relatives (Rac in animals, Rop in plants), are crucial for controlling polarization. Polarization signals act through Cdc42 regulators to accumulate Cdc42-GTP at the future cell front. Cdc42-GTP then organizes the cytoskeleton via various effectors, shaping the polarized morphology of the cell 3,4 . Understanding the molecular details of polarity is essential for understanding various diseases, as disruptions in polarity mechanisms are often linked to cancer, neurodegenerative disorders, and immune system deficiencies 5,6 .
The discovery that bacterial cells are also polarized dates back to the first electron micrograph showing flagella at the cell poles of bacteria. Since then, efforts to study polarity-based mechanisms on model organisms including B. subtilis, C. crescentus, and E. coli have offered fundamental insights into the mechanisms underlying the
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BibTeX
@article{dinet2026cell,
title = {{Cell polarity control by an unconventional G-protein complex in bacteria}},
author = {Céline Dinet and Corinne Sebban-Kreuzer and Deborah Byrne-Kodjabachian and Sébastien Lhospice and Julien Herrou and Fabien Durbesson and Renaud Vincentelli and Vincent Calvez and James N. Sturgis and Alphée Michelot and Tâm Mignot},
journal = {Nature Communications},
year = {2026},
month = jun,
doi = {10.1038/s41467-026-74081-1},
url = {https://amu.hal.science/hal-05738265v1},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - JOUR
TI - Cell polarity control by an unconventional G-protein complex in bacteria
AU - Céline Dinet
AU - Corinne Sebban-Kreuzer
AU - Deborah Byrne-Kodjabachian
AU - Sébastien Lhospice
AU - Julien Herrou
AU - Fabien Durbesson
AU - Renaud Vincentelli
AU - Vincent Calvez
AU - James N. Sturgis
AU - Alphée Michelot
AU - Tâm Mignot
PY - 2026
DA - 2026/06/15
JO - Nature Communications
DO - 10.1038/s41467-026-74081-1
UR - https://amu.hal.science/hal-05738265v1
AB - In Myxococcus xanthus, a predatory soil bacterium, cell polarity and motility are regulated by MglA (a small GTPase) and its regulators, MglB (a potential GAP) and RomRX (a previously proposed GEF), but their precise roles remain unclear. Using fluorescent nucleotides suitable for fluorescence anisotropy measurements, we show that RomRX does not function as a GEF but instead acts as an effector binding MglA GTP . We further find, using an enzymatic model, that MglB exhibits both GAP and GEF properties depending on the local MglA GDP concentration. Additionally, RomRX, specifically RomR, effectively dissociates the MglA-MglB complex by sequestering MglB. This low-affinity interaction permits GAP activity while still partitioning the proteins in vivo, as shown by a biomimetic oil-emulsion droplet assay in a cell-sized system. A minimal mathematical model incorporating these interactions and previous findings recapitulates how dynamic interactions between these three players form an invertible polarity axis in the M. xanthus cell. Cell polarity, the asymmetric organization of cellular components, is a fundamental characteristic of many living organisms. It is essential for effective cell motility and a myriad of other directional functions, such as epithelial transport, neuronal signaling, and body axis specification in embryos 1,2 . A polarized cell establishes a distinct axis with a specific front, known as the polarity site, enabling it to maintain functionally distinct domains. This ability relies on intricate interactions between various protein complexes, including small GTPases, polarity proteins, and cytoskeletal components, that regulate multiple signaling pathways. In most eukaryotic cells, small GTPases of the Ras superfamily act as molecular switches in many signaling pathways and play a central role in cell polarization processes. For example, the Rho-family GTPases, including Cdc42 (one of the most highly conserved GTPases) and its relatives (Rac in animals, Rop in plants), are crucial for controlling polarization. Polarization signals act through Cdc42 regulators to accumulate Cdc42-GTP at the future cell front. Cdc42-GTP then organizes the cytoskeleton via various effectors, shaping the polarized morphology of the cell 3,4 . Understanding the molecular details of polarity is essential for understanding various diseases, as disruptions in polarity mechanisms are often linked to cancer, neurodegenerative disorders, and immune system deficiencies 5,6 . The discovery that bacterial cells are also polarized dates back to the first electron micrograph showing flagella at the cell poles of bacteria. Since then, efforts to study polarity-based mechanisms on model organisms including B. subtilis, C. crescentus, and E. coli have offered fundamental insights into the mechanisms underlying the
SN - 2041-1723
SN - 2041-1723
ER -