CLONING AND CHARACTERIZATION OF MOTY, A GENE CODING FOR A COMPONENT OF THE SODIUM-DRIVEN FLAGELLAR MOTOR IN VIBRIO-ALGINOLYTICUS

The bacterial flagellar motor is a molecular machine that couples prot on or sodium influx to force generation for driving rotation of the he lical flagellar filament. In this study, we cloned a gene (motY) encod ing a component of the sodium-driven polar flagellar motor in Vibrio a lginolyticus. Nucleotide sequence analysis revealed that the gene enco des a 293-amino-acid polypeptide with a single putative transmembrane segment that is very similar (94.5% identity) to the recently describe d MotY of V. parahaemolyticus. Their C-terminal domains were similar t o the C-terminal domains of many peptidoglycan-interacting proteins, e .g., Escherichia coli MotB and OmpA, suggesting that MotY may interact with peptidoglycan for anchoring the motor. By using the lac promoter -repressor system, motY expression was controlled in V. alginolyticus cells, Swimming ability increased with increasing concentrations of th e inducer isopropyl-beta-D-thiogalactopyranoside, and the swimming fra ction increased after induction. These results are consistent with the notion that MotY is a component of the force-generating unit. V. algi nolyticus motY complemented the motY mutation of V. parahaemolyticus. However, motY appeared to lack a region corresponding to the proposed motY promoter of V. parahaemolyticus. Instead, sequences similar to th e sigma(54) consensus were found in the upstream regions of both speci es. We propose that they are transcribed from the sigma(54)-specific p romoters.