These findings show that the flagellar secretion apparatus functions as a proton-driven protein exporter and that ATP hydrolysis is not essential for type III secretion. Weak swarming motility and rare flagella were observed in a mutant deleted for FliI and for the non-flagellar type-III secretion ATPases InvJ and SsaN. The export of several flagellar export substrates was prevented by treatment with the protonophore CCCP, with no accompanying decrease in cellular ATP levels. Here we show that flagellar secretion in Salmonella enterica requires the proton motive force (PMF) and does not require ATP hydrolysis by FliI. The flagellar secretion apparatus comprises a membrane-embedded complex of about five proteins, and soluble factors, which include export-dedicated chaperones and an ATPase, FliI, that was thought to provide the energy for export. Mitochondria maintain a proton gradient across the inner mitochondrial membrane. All prokaryotic cells (Bacteria and Archaea) maintain a proton gradient (pH gradient) across their plasma membranes. The resulting influx of protons that occurs during this type of coupled transport must be countered by the active pumping of protons back out to the exterior. This apparatus is related to the injectisome used by many gram-negative pathogens and symbionts to transfer effector proteins into host cells in both systems this export mechanism is termed 'type III' secretion. The proton-motive force is a combination of a difference in proton (H+ ion) concentrations across a membrane, and the resulting electrical potential. the lactose symporter (LacY) The lactose symporter cotransports lactose and H+ ions into the cell using energy stored in the proton motive force. Biosensor Chemotaxis Mechanosensing Proton motive force Single molecular. Motors rotational speed is linearly proportional to the electrochemical gradients of either proton or sodium driving ions, while its direction is regulated by the chemotactic network. Bacterial flagella contain a specialized secretion apparatus that functions to deliver the protein subunits that form the filament and other structures to outside the membrane. Bacterial Flagellar Motor is one of natures rare rotary molecular machines.
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