4QRM

crystal structure of a binary complex of FliM-FliG middle domains from T.maritima

Summary for 4QRM

• Entry DOI: 10.2210/pdb4qrm/pdb
• Descriptor: Flagellar motor switch protein FliM, Flagellar motor switch protein FliG (2 entities in total)
• Functional Keywords: flagellar rotor proteins, protein binding
• Biological source: Thermotoga maritima; More
• Cellular location: Cell inner membrane ; Peripheral membrane protein : Q9WZE6; Cell inner membrane ; Peripheral membrane protein ; Cytoplasmic side : Q9WY63
• Total number of polymer chains: 22
• Total formula weight: 323750.42

Authors

Crane, B.R.,Sircar, R. (deposition date: 2014-07-01, release date: 2015-06-10, Last modification date: 2024-02-28)

Primary citation

Sircar, R.,Borbat, P.P.,Lynch, M.J.,Bhatnagar, J.,Beyersdorf, M.S.,Halkides, C.J.,Freed, J.H.,Crane, B.R.
Assembly states of FliM and FliG within the flagellar switch complex.
J.Mol.Biol., 427:867-886, 2015

PubMed Abstract: At the base of the bacterial flagella, a cytoplasmic rotor (the C-ring) generates torque and reverses rotation sense in response to stimuli. The bulk of the C-ring forms from many copies of the proteins FliG, FliM, and FliN, which together constitute the switch complex. To help resolve outstanding issues regarding C-ring architecture, we have investigated interactions between FliM and FliG from Thermotoga maritima with X-ray crystallography and pulsed dipolar ESR spectroscopy (PDS). A new crystal structure of an 11-unit FliG:FliM complex produces a large arc with a curvature consistent with the dimensions of the C-ring. Previously determined structures along with this new structure provided a basis to test switch complex assembly models. PDS combined with mutational studies and targeted cross-linking reveal that FliM and FliG interact through their middle domains to form both parallel and antiparallel arrangements in solution. Residue substitutions at predicted interfaces disrupt higher-order complexes that are primarily mediated by contacts between the C-terminal domain of FliG and the middle domain of a neighboring FliG molecule. Spin separations among multi-labeled components fit a self-consistent model that agree well with electron microscopy images of the C-ring. An activated form of the response regulator CheY destabilizes the parallel arrangement of FliM molecules to perturb FliG alignment in a process that may reflect the onset of rotation switching. These data suggest a model of C-ring assembly in which intermolecular contacts among FliG domains provide a template for FliM assembly and cooperative transitions.

PubMed: 25536293
DOI: 10.1016/j.jmb.2014.12.009

Experimental method

X-RAY DIFFRACTION (4.315 Å)