MOTY, A COMPONENT OF THE SODIUM-TYPE FLAGELLAR MOTOR

Energy to power the rotation of bacterial flagella can be derived from the proton or sodium transmembrane potential. Until new, genes encodi ng a bacterial sodium-type flagellar motor have not been defined. A ge ne, motY, encoding one component of the sodium-type flagellar motor of Vibrio parahaemolyticus was cloned by complementation of a Mot(-) mut ant strain. Sequencing revealed an open reading frame of 879 nucleotid es in which a transposon conferring a motility defect mapped. Overexpr ession of motY in Escherichia coli allowed identification of a product 33 kDa in apparent size on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This size correlated well with the predicted molecula r mass of 33,385 Da. Unlike mot genes identified in other bacterial lo calized transposon mutagenesis suggested that the locus was not an ext ended region containing multiple genes required for swimming motility. Sequencing upstream and downstream of motY confirmed that the gene ma ps alone and placed it within a locus homologous to the E. coli mt loc us. Although data bank searches failed to reveal significant similarit y to known motility components, the carboxyl terminus of MotY showed e xtensive homology to a number of outer membrane proteins known to inte ract with peptidoglycan, including OmpA and peptidoglycan-associated l ipoproteins. To a limited extent, this domain could also be identified in the Bacillus subtilis MotB protein. This finding suggests that Mot Y plays the role of a stator in the sodium flagellar motor, stabilizin g the farce-generating unit through direct interaction with the cell w all.