9N4Z

CCW Flagellar Switch Complex - FliF, FliG, FliM, and FliN forming 34-mer C-ring from Salmonella

This is a non-PDB format compatible entry.

Replaces:  8T8O

Summary for 9N4Z

• Entry DOI: 10.2210/pdb9n4z/pdb
• Related: 9N49
• EMDB information: 48916
• Descriptor: Flagellar M-ring protein, Flagellar motor switch protein FliG, Flagellar motor switch protein FliM, ... (4 entities in total)
• Functional Keywords: c-ring, bacterial, chemotaxis, c ring, flagellar motor complex, switch complex, flig, flim, flin, flif, motor protein
• Biological source: Salmonella enterica subsp. enterica serovar Typhimurium; More
• Total number of polymer chains: 204
• Total formula weight: 6136766.66

Authors

Singh, P.K.,Iverson, T.M. (deposition date: 2025-02-03, release date: 2025-03-19, Last modification date: 2025-04-02)

Primary citation

Singh, P.K.,Iverson, T.M.
Improving CryoEM maps of symmetry-mismatched macromolecular assemblies: A case study on the flagellar motor.
J.Struct.Biol., 217:108184-108184, 2025

PubMed Abstract: Advances in cryo-electron microscopy instrumentation and sample preparation have significantly improved the ability to collect quality data for biomolecular structures. However, achieving resolutions consistent with data quality remains challenging in structures with symmetry mismatches. As a case study, the bacterial flagellar motor is a large complex essential for bacterial chemotaxis and virulence. This motor contains a smaller membrane-supramembrane ring (MS-ring) and a larger cytoplasmic ring (C-ring). These two features have a 33:34 symmetry mismatch when expressed in E. coli. Because close symmetry mismatches are the most difficult to deconvolute, this makes the flagellar motor an excellent model system to evaluate refinement strategies for symmetry mismatch. We compared the performance of masked refinement, local refinement, and particle subtracted refinement on the same data. We found that particle subtraction prior to refinement was essential for correctly deconvoluting the symmetry of the smaller MS-ring. Additional processing resulted in final resolutions of 3.1 Å for the MS-ring and 3.0 Å for the C-ring, which improves the resolution of the MS-ring by 0.3 Å and the resolution of the C-ring by 1.0 Å as compared to past work. Although particle subtraction is fairly well-established, it is rarely applied to problems of symmetry mismatch, making this case study a valuable demonstration of its utility in this context.

PubMed: 40054642
DOI: 10.1016/j.jsb.2025.108184

Experimental method

ELECTRON MICROSCOPY (3 Å)