title: Interactions of bacterial flagellar chaperone-substrate complexes with FlhA contribute to co-ordinating assembly of the flagellar filament.
abstract: Assembly of the bacterial flagellar filament is strictly sequential; the junction proteins, FlgK and FlgL, are assembled at the distal end of the hook prior to the FliD cap, which supports assembly of as many as 30 000 FliC molecules into the filament. Export of these proteins requires assistance of flagellar chaperones: FlgN for FlgK and FlgL, FliT for FliD and FliS for FliC. The C-terminal cytoplasmic domain of FlhA (FlhAC ), a membrane component of the export apparatus, provides a binding-site for these chaperone-substrate complexes but it remains unknown how it co-ordinates flagellar protein export. Here, we report that the highly conserved hydrophobic dimple of FlhAC is involved in the export of FlgK, FlgL, FliD and FliC but not in proteins responsible for the structure and assembly of the hook, and that the binding affinity of FlhAC for the FlgN/FlgK complex is slightly higher than that for the FliT/FliD complex and about 14-fold higher than that for the FliS/FliC complex, leading to the proposal that the different binding affinities of FlhAC for these chaperone/substrate complexes may confer an advantage for the efficient formation of the junction and cap structures at the tip of the hook prior to filament formation.
authors: Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan.
authors: Miki
authors: M
authors: Kinoshita
authors: Noritaka
authors: N
authors: Hara
authors: Katsumi
authors: K
authors: Imada
authors: Keiichi
authors: K
authors: Namba
authors: Tohru
authors: T
authors: Minamino
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D017124:Conserved Sequence; D005407:Flagella / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D018832:Molecular Chaperones / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D055503:Protein Multimerization; D021381:Protein Transport; D012486:Salmonella typhimurium / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; C088595:FlgK protein, Bacteria; C087498:FlgN protein, Bacteria; C080688:FlhA protein, Bacteria; D008565:Membrane Proteins; D018832:Molecular Chaperones; C076733:FlaD protein, Bacteria; C076734:FliS protein, Bacteria; C076735:fliT protein, Bacteria