Co-Folding of a FliF-FliG Split Domain Forms the Basis of the MS:C Ring Interface within the Bacterial Flagellar Motor.

Publication Type:

Journal Article


Structure, Volume 25, Issue 2, p.317-328 (2017)


Amino Acid Motifs, Bacterial Proteins, Binding Sites, Biomechanical Phenomena, Cell Membrane, Cloning, Molecular, Crystallography, X-Ray, Escherichia coli, Flagella, Gene Expression, Membrane Proteins, Models, Molecular, Protein Binding, Protein Conformation, alpha-Helical, Protein Folding, Protein Interaction Domains and Motifs, Protein Structure, Tertiary, Recombinant Fusion Proteins, Thermotoga maritima


<p>The interface between the membrane (MS) and cytoplasmic (C) rings of the bacterial flagellar motor couples torque generation to rotation within the membrane. The structure of the C-terminal helices of the integral membrane protein FliF (FliFC) bound to the N terminal domain of the switch complex protein FliG (FliGN) reveals that FliGN folds around FliFC to produce a topology that closely resembles both the middle and C-terminal domains of FliG. The interface is consistent&nbsp;with solution-state nuclear magnetic resonance, small-angle X-ray scattering, in&nbsp;vivo interaction studies, and cellular motility assays. Co-folding with FliFC induces substantial conformational changes in FliGN and suggests that FliF and FliG have the same&nbsp;stoichiometry within the rotor. Modeling the FliFC:FliGN complex into cryo-electron microscopy rotor density updates the architecture of the middle and upper switch complex and shows how domain shuffling of a conserved interaction module anchors the cytoplasmic rotor to the membrane.</p>