36HU
Salmonella Flagellar Export Gate with FlhB in the context of the intact basal body
This is a non-PDB format compatible entry.
Summary for 36HU
| Entry DOI | 10.2210/pdb36hu/pdb |
| EMDB information | 77586 |
| Descriptor | Flagellar biosynthetic protein FliP, Flagellar biosynthetic protein FliR, Flagellar biosynthetic protein FliQ, ... (4 entities in total) |
| Functional Keywords | flagella, secretion, pmf, protein transport |
| Biological source | Salmonella enterica subsp. enterica serovar Typhimurium More |
| Total number of polymer chains | 11 |
| Total formula weight | 243779.21 |
| Authors | |
| Primary citation | Johnson, M.K.,Johnson, S.,Deme, J.C.,Alfaro-Alvarado, L.,Bryant, O.J.,Chevance, F.F.V.,Hughes, K.T.,Lea, S.M. Structure of the proton-powered secretion motor at the heart of the bacterial flagellum. Biorxiv, 2026 Cited by PubMed Abstract: Bacterial type III secretion systems export proteins across the inner membrane using the proton-motive force (PMF), but how proton flow is coupled to opening of the export channel is unknown. Here we present single-particle cryo-EM structures at 2.5-4.2 Å resolution of the intact flagellar Export Apparatus from , obtained using optimized extraction conditions of the endogenous assembly that retain the complete transmembrane complex. The transmembrane domain of FlhA forms a nonameric funnel-shaped basket beneath the Export Gate, with each subunit harboring a buried pathway of conserved hydrophilic residues spanning the hydrophobic core of the membrane. FlhB is resolved for the first time within the intact gate, revealing helices that thread through the FlhA channel, completely sealing it at rest. A symmetry-free reconstruction captures one FlhA protomer hinged outward at the water-filled cavity, breaking the rotational symmetry. Together, these structures define the architecture of the proton-transducing element of the type III secretion system and suggest a rotary gating mechanism, with parallels to the F motor of ATP synthase, in which PMF-driven conformational cycling of FlhA drives regulated opening of the export channel. PubMed: 42367960DOI: 10.64898/2026.06.13.732081 PDB entries with the same primary citation |
| Experimental method | ELECTRON MICROSCOPY (2.5 Å) |
Structure validation
Download full validation report
