![]() ![]() The rate of the protein export is markedly low in the absence of FliH, FliI and FliJ, although these components are not essential because flagellar formation occasionally occurs in their absence 13, 14, 15, 16. Recently, it has become apparent that FliH, FliI and FliJ are evolutionarily related to components of F OF 1-ATP synthase, which utilizes PMF for ATP synthesis 5, 7, 8, 9.įliI is an ATPase 10 and forms a complex with FliH and FliJ 11, 12, 13. These components of the export apparatus share substantial sequence and functional similarities with those of the type III secretion system of pathogenic bacteria, which directly inject virulence factors into their host cells 6. The export apparatus consists of three soluble proteins, FliH, FliI and FliJ, and six integral membrane proteins, FlhA, FlhB, FliO, FliP, FliQ and FliR 3, 4, 5. For construction of the flagellum, many of the flagellar component proteins are transported to the distal end of the flagellar structure by the flagellar type III protein export apparatus. ![]() Flagellar assembly begins with the basal body, followed by the hook and finally the filament. The bacterial flagellum, which is responsible for motility, consists of at least three substructures: the basal body, the hook and the filament. Although Δψ and ΔpH are equivalent driving forces for proton movement and translocation in physics and have also been believed to have equivalent roles in biological functions, recent experimental data suggest a differential usage of Δψ and ΔpH in biological processes, such as flagellar motor rotation 1 and ATP synthesis 2. PMF consists of two components: the electric potential difference (Δψ) and the proton concentration difference (ΔpH). Proton motive force (PMF), the electrochemical potential difference of protons across a biological membrane, is utilized as the energy source of many biological activities, including protein export, ATP synthesis and flagellar motor rotation. ![]()
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