التفاصيل البيبلوغرافية
| العنوان: |
Assembly States of FliM and FliG within the Flagellar Switch Complex. |
| المؤلفون: |
Sircar, Ria1, Borbat, Peter P.1,2, Lynch, Michael J.1, Bhatnagar, Jaya1, Beyersdorf, Matthew S.3, Halkides, Christopher J.3, Freed, Jack H.1,2, Crane, Brian R.1 bc69@cornell.edu |
| المصدر: |
Journal of Molecular Biology. Feb2015, Vol. 427 Issue 4, p867-886. 20p. |
| مصطلحات موضوعية: |
*BACTERIAL flagella, *X-ray crystallography, *GENETIC mutation, *ELECTRON paramagnetic resonance spectroscopy, *CRYSTAL structure, *ELECTRON microscopy, *INTERFACES (Physical sciences) |
| مستخلص: |
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. [ABSTRACT FROM AUTHOR] |
| قاعدة البيانات: |
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