Long-range coupling regulates stator dynamics in the bacterial flagellar motor

Area of Science:

• Microbiology
• Biophysics
• Molecular Biology

Background:

• Bacterial flagellar motors generate torque via stator complexes.
• Stator complexes, composed of MotA and MotB proteins, anchor to peptidoglycan.
• The mechanism by which external load regulates stator anchoring is not fully understood.

Purpose of the Study:

• To investigate how the periplasmic domain of MotB in *Escherichia coli* regulates stator dynamics.
• To elucidate the role of long-range couplings and flexibility within MotB in stator anchoring and motor function.

Main Methods:

• Computational modeling to predict dynamic couplings within the MotB periplasmic domain.
• Coevolutionary analysis to identify conserved communication pathways.
• Site-directed mutagenesis of *E. coli* MotB and assessment of bacterial motility phenotypes.
• Molecular dynamics simulations to correlate loop flexibility with *in vivo* swimming speeds.

Main Results:

• Long-range couplings within the MotB periplasmic domain were identified and computationally modeled.
• Mutations at key sites in MotB altered stator dynamics and bacterial swimming phenotypes.
• Simulations showed a strong correlation between the dynamic flexibility of MotB loops and observed swimming speeds.
• These findings indicate that MotB's flexibility and internal couplings tune stator anchoring.

Conclusions:

• Flexibility and long-range couplings within the *E. coli* MotB periplasmic domain are critical for regulating stator anchoring.
• This mechanosensitive remodeling of stator anchoring provides insight into bacterial flagellar motor adaptation to load.