2-deoxygalactose, a specific substrate of the Salmonella typhiimurium galactose permease: its use for the isolation of galP mutants.
2-Deoxygalactose is a specific substrate of the galactose permease. The apparent Km is about 500 micron, compared to 45 micron for galactose, whereas the maximal rate of uptake is one-half to one-third of that of galactose. None of the other galactose transport systems, including methyl beta-D-thiogalactosides I and II, the beta-methyl-galactoside permease, and both arabinose systems, is able to catalyze transport of 2-deoxygalactose to a significant extent. 2-Deoxygalactose can also be used to isolate mutants defective in galactose permease, since it is bacteriostatic. Colonies that grow with lactate, malate, or succinate as a carbon source in the presence of 0.5 to 2 mM 2-doexygalactose were found to be mostly galP mutants, lacking galactose permease. Spontaneous 2-deoxygalactose-resistant strains arose with a frequency of about 2 X 10(-6). galP mutants have also been derived from pts deletion mutants that require galactose permease for growth on glucose. Revertants have been obtained that have acquired the parental phenotype.
D001692:Biological Transport; D005643:Fucose / Q000378:metabolism*; D005838:Genotype; D007700:Kinetics; D026901:Membrane Transport Proteins / Q000378:metabolism*; D009154:Mutation; D009876:Operon; D012486:Salmonella typhimurium / Q000201:enzymology* / Q000235:genetics; D013379:Substrate Specificity
D026901:Membrane Transport Proteins; D005643:Fucose