Molecular Cloning and Genetic Characterization of a Mutation Encoding Proline Over-production

摘要: A mutation encoding proline over-production that confers enhanced osmotic tolerance on S. typhimurium is closely linked to the proBA biosynthetic genes. The proline over-producing mutation of an osmotolerant mutant of S. typhimurium was cloned in Escherichia coli. A11 transformants obtained with the DNA from the osmotolerant mutant had the proline over-producing, osmotolerant phenotype, whereas all transformants obtained with DNA from the sensitive parental strain were not proline over-producing, and not osmotically tolerant. The genes that code for the enzymes, gamma-glutamyl kinase (proB), and for gamma-glutamyl phosphate dehydrogenase (proA), were identified genetically by transposon (Tn5) insertion and complementation experiments. The Tn5 insertions were also used to genetically characterize the proline over-producing mutation. The possible mechanism and propects for the mutation encoding proline over-production are discussed.