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1.
EMBO J ; 42(1): e111661, 2023 01 04.
Artigo em Inglês | MEDLINE | ID: mdl-36345779

RESUMO

In rod-shaped bacteria, type IV pili (Tfp) promote twitching motility by assembling and retracting at the cell pole. In Myxococcus xanthus, a bacterium that moves in highly coordinated cell groups, Tfp are activated by a polar activator protein, SgmX. However, while it is known that the Ras-like protein MglA is required for unipolar targeting, how SgmX accesses the cell pole to activate Tfp is unknown. Here, we demonstrate that a polar beacon protein, FrzS, recruits SgmX at the cell pole. We identified two main functional domains, including a Tfp-activating domain and a polar-binding domain. Within the latter, we show that the direct binding of MglA-GTP unveils a hidden motif that binds directly to the FrzS N-terminal response regulator (CheY). Structural analyses reveal that this binding occurs through a novel binding interface for response regulator domains. In conclusion, the findings unveil the protein interaction network leading to the spatial activation of Tfp at the cell pole. This tripartite system is at the root of complex collective behaviours in this predatory bacterium.


Assuntos
Proteínas de Bactérias , Myxococcus xanthus , Proteínas de Bactérias/genética , Proteínas de Bactérias/química , Myxococcus xanthus/metabolismo , Fímbrias Bacterianas/química
2.
Proc Natl Acad Sci U S A ; 117(45): 28366-28373, 2020 11 10.
Artigo em Inglês | MEDLINE | ID: mdl-33093210

RESUMO

Type IV pili (Tfp) are highly conserved macromolecular structures that fulfill diverse cellular functions, such as adhesion to host cells, the import of extracellular DNA, kin recognition, and cell motility (twitching). Outstandingly, twitching motility enables a poorly understood process by which highly coordinated groups of hundreds of cells move in cooperative manner, providing a basis for multicellular behaviors, such as biofilm formation. In the social bacteria Myxococcus xanthus, we know that twitching motility is under the dependence of the small GTPase MglA, but the underlying molecular mechanisms remain elusive. Here we show that MglA complexed to GTP recruits a newly characterized Tfp regulator, termed SgmX, to activate Tfp machines at the bacterial cell pole. This mechanism also ensures spatial regulation of Tfp, explaining how MglA switching provokes directional reversals. This discovery paves the way to elucidate how polar Tfp machines are regulated to coordinate multicellular movements, a conserved feature in twitching bacteria.


Assuntos
Proteínas de Bactérias/metabolismo , Fímbrias Bacterianas/metabolismo , Proteínas Monoméricas de Ligação ao GTP/metabolismo , Myxococcus xanthus/fisiologia , Proteínas de Bactérias/genética , Polaridade Celular/fisiologia , Myxococcus xanthus/citologia , Myxococcus xanthus/genética , Polimorfismo de Nucleotídeo Único , Sequenciamento Completo do Genoma
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