title: Co-Folding of a FliF-FliG Split Domain Forms the Basis of the MS:C Ring Interface within the Bacterial Flagellar Motor.
abstract: 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 FliGNfolds around FliFCto produce a topology that closely resembles both the middle and C-terminal domains of FliG. The interface is consistent with solution-state nuclear magnetic resonance, small-angle X-ray scattering, in vivo interaction studies, and cellular motility assays. Co-folding with FliFCinduces substantial conformational changes in FliGNand suggests that FliF and FliG have the same stoichiometry within the rotor. Modeling the FliFC:FliGNcomplex 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.
authors.affiliation: Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Lynch
authors.affiliation: Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, CA 93106-9510, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Levenson
authors.affiliation: Department of Biology, University of Utah, Salt Lake City, UT 84112, USA.
authors.forename: Eun A
authors.initials: EA
authors.lastname: Kim
authors.affiliation: Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Ria
authors.initials: R
authors.lastname: Sircar
authors.affiliation: Department of Biology, University of Utah, Salt Lake City, UT 84112, USA.
authors.forename: David F
authors.initials: DF
authors.lastname: Blair
authors.affiliation: Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, CA 93106-9510, USA.
authors.forename: Frederick W
authors.initials: FW
authors.lastname: Dahlquist
authors.affiliation: Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA. Electronic address: bc69@cornell.edu.
authors.forename: Brian R
authors.initials: BR
authors.lastname: Crane
mesh_terms: D020816:Amino Acid Motifs; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D001696:Biomechanical Phenomena; D002462:Cell Membrane / Q000737:chemistry* / Q000648:ultrastructure; D003001:Cloning, Molecular; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005407:Flagella / Q000737:chemistry* / Q000648:ultrastructure; D015870:Gene Expression; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D011485:Protein Binding; D000072756:Protein Conformation, alpha-Helical; D017510:Protein Folding; D054730:Protein Interaction Domains and Motifs; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D020124:Thermotoga maritima / Q000737:chemistry* / Q000648:ultrastructure
chemical_list: D001426:Bacterial Proteins; C075661:Flif protein, Bacteria; C075660:Flig protein, Bacteria; D008565:Membrane Proteins; D011993:Recombinant Fusion Proteins
keywords: X-ray structure; assembly; chemotaxis; cross-linking; domain shuffling; flagellar motor; molecular machine; motility; switch complex