| Description |
Type III secretion system in bacteria flagella functions to transfer the protein subunits that form the filament and other structures to outside the membrane. This apparatus membrane is mainly composed of FlhA, FlhB, FliO, FliP, FliQ and FliR, which form the export gate complex, while the delivery is offered by FliH2-FliI complex in cytoplasm engernized by PMF. FlhA, FlhB, FliP are essential proteins for apparatus fuctioning. Further studies are performed to get more information about the roles of proteins mentioned. Mutagenesis of Flip by tryptophan shows some positions can not tolerate bulky substitutions, while mutant FlhA shows different function when substituted with differently charged residues. The results show that residues Asp 158 and Asp 208 of FlhA are important for flagellar export. Certain of the Asp 208 replacements, but not the Asp 158 replacements, could be suppressed by mutations in other residues of FlhA; thus, the requirement for an acidic residue appears most strict at position 158. The results are discussed in the framework of a transport mechanism based on proton-driven conformational changes in cytoplasmic domains of FlhA. |
