Switch Interactions Control Energy Frustration and Multiple Flagellar Filament Structures

Bacterial flagellar filament is a macromolecular assembly consisting of a single protein, flagellin. Bacterial swimming is controlled by the conformational transitions of this filament between left-and right-handed supercoils induced by the flagellar motor torque. We present a massive molecular dyna...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2006-03, Vol.103 (13), p.4894-4899
Main Authors: Kitao, Akio, Yonekura, Koji, Maki-Yonekura, Saori, Samatey, Fadel A., Imada, Katsumi, Namba, Keiichi, Go, Nobuhiro
Format: Article
Language:English
Subjects:
Atomic interactions
Atoms
Bacteria
Biological Sciences
Biology
Biophysics
Computer Simulation
Curvature
Flagella - chemistry
Flagella - genetics
Flagella - metabolism
Hydrogen bonds
Modeling
Models, Molecular
Molecular structure
Motors
Polymorphism
Protein Binding
Protein Structure, Quaternary
Protein Structure, Tertiary
Protein Subunits - chemistry
Protein Subunits - genetics
Protein Subunits - metabolism
Research facilities
Salmonella typhimurium - chemistry
Salmonella typhimurium - genetics
Salmonella typhimurium - metabolism
Salts
Simulation
Simulations
Torque
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Summary:Bacterial flagellar filament is a macromolecular assembly consisting of a single protein, flagellin. Bacterial swimming is controlled by the conformational transitions of this filament between left-and right-handed supercoils induced by the flagellar motor torque. We present a massive molecular dynamics simulation that was successful in constructing the atomic-level supercoil structures consistent with various experimental data and further in elucidating the detailed underlying molecular mechanisms of the polymorphic supercoiling. We have found that the following three types of interactions are keys to understanding the supercoiling mechanism. "Permanent" interactions are always maintained between subunits in the various supercoil structures. "Sliding" interactions are formed between variable hydrophilic or hydrophobic residue pairs, allowing intersubunit shear without large change in energy. The formation and breakage of "switch" interactions stabilize inter- and intrasubunit interactions, respectively. We conclude that polymorphic supercoiling is due to the energy frustration between them. The transition between supercoils is achieved by a "transform and relax" mechanism: the filament structure is geometrically transformed rapidly and then slowly relaxes to energetically metastable states by rearranging interactions.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.0510285103