The identification of the mot gene product with Escherichia coli-lambda hybrids

Molecular cloning techniques were used to construct lambda-E. coli hybrid bacteriophage carrying genes involved in bacterial flagellar motility (mot) and chemotaxis (cheA). A series of hybrid bacteriophage without each of these genes was also prepared. When paralyzed mutants of E. coli were infected with lambda that carried the mot gene, the ability of the bacterium to swim was rapidly restored. The restoration of motility was the result of the synthesis and insertion into the cell membrane of a protein with an apparent molecular weight of 31,000 (the Mot protein). Another polypeptide with a mobility on acrylamide gel electrophoresis which corresponded to a molecular weight of 39,000 was associated with the cheA gene. The presence of this polypeptide alone was not sufficient to restore chemotactic activity to mutant cheA strains. It was suggested that only a portion of the cheA gene was cloned, and thus the 39,000 protein may be a partial product of the cheA gene, or the product of a second mot gene.