MreB Filaments in the Elongasome Modulate E. coli Membrane Curvature.

MreB, a bacterial actin homolog, plays a pivotal role in defining the shape of rod-shaped bacteria by coordinating peptidoglycan synthesis during cell elongation. It forms filaments that interact with the cytosolic leaflet of the cell membrane, as well as with membrane proteins and other cytosolic proteins. In this study, molecular dynamics (MD) simulations were used to investigate the interactions between Escherichia coli (E. coli) MreB and model cytoplasmic membranes. The simulations reveal that MreB filaments recruit cardiolipin and induce membrane bending toward the periplasmic space. Cardiolipin exhibits a concentration-dependent effect on bending, highlighting its critical role in this mechanism. Simulations with MreB mutants identify residues R105 and R136 as key contributors to both cardiolipin recruitment and membrane bending. Additionally, removal of the N-terminal helix in E. coli MreB was shown to reduce membrane bending. This study concludes that MreB induces membrane bending through two distinct mechanisms: (1) recruitment of the cone-shaped lipid cardiolipin and (2) physical distortion by the N-terminal helix. These findings uncover a novel mechanism by which MreB alters membrane architecture, offering insights into how other proteins are recruited to the filament in the E. coli elongasome.