Steady-state helices of the actin homolog MreB inside bacteria: dynamics without motors.
Within individual bacteria, we combine force-dependent polymerization dynamics of individual MreB protofilaments with an elastic model of protofilament bundles buckled into helical configurations. We use variational techniques and stochastic simulations to relate the pitch of the MreB helix, the total abundance of MreB, and the number of protofilaments. By comparing our simulations with mean-field calculations, we find that stochastic fluctuations are significant. We examine the quasistatic evolution of the helical pitch with cell growth, as well as time scales of helix turnover and de novo establishment. We find that while the body of a polarized MreB helix treadmills toward its slow-growing end, the fast-growing tips of laterally associated protofilaments move toward the opposite fast-growing end of the MreB helix. This offers a possible mechanism for targeted polar localization without cytoplasmic motor proteins.
Allard
Jun F
JF
Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada B3H 3J5.
Rutenberg
Andrew D
AD
D008841:Actin Cytoskeleton / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D000199:Actins / Q000737:chemistry / Q000235:genetics / Q000502:physiology* / Q000648:ultrastructure; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology* / Q000648:ultrastructure; D001692:Biological Transport; D007700:Kinetics; D008954:Models, Biological; D009068:Movement; D011108:Polymers / Q000737:chemistry; D017433:Protein Structure, Secondary; D013269:Stochastic Processes
D000199:Actins; D001426:Bacterial Proteins; D011108:Polymers