Molecular analysis of the export-switching apparatus of the anti-sigma factor which regulates the bacterial flagellar regulon

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1. FlgJ protein was shown to have a muramidase activity involved in penetration process of the peptidoglycan layer by the rod structure. FlgA was shown to be a periplasmic chaperone essential for P-ring formation.2. N-terminal one third of the FlgD protein was shown to be involved in modulation of hook assembly, whereas its C terminal portion was found to enhance the translation and export of the hook protein. This suggests that the monitor system of hook completion may depend upon the FlgD-mediated coupling of translation of the hook protein to its export.3. The FlgM export gate was found to be turned on at the initiation step of hook assembly. This suggests that hook assembly may be carried out with the pool of hook protein which has been already incorporated into the export apparatus by the initiation step of hook assembly.4. Northern blotting analysis found a 200-base RNA molecule derived from the flgB mRNA. The length of this RNA corresponds to axial length of the basal body-hook structure, suggesting that this RNA may be involved in the hook length control. Expression analysis of the fliC-lacZ translational fusion revealed that its expression is slightly repressed after hook assembly. This suggests that translation-controlling machinery of the fliC gene may be established on hook completion.