title: Analysis of melibiose mutants deficient in alpha-galactosidase and thiomethylgalactoside permease II in Escherichia coli K-12.
abstract: Three types of mutants (mel(-)) unable to metabolize the alpha-d-galactoside, melibiose, were derived from Escherichia coli K-12. One type lacked alpha-galactosidase; another lacked a specific transport system, termed thiomethylgalactoside (TMG) permease II; and the third lacked both of these functions. The mutational sites were genetically mapped by recombination frequency with different markers and by determination of chromosomal transfer in interrupted-mating experiments. All three mel(-) mutant types mapped in a cluster near to the metA marker on the E. coli chromosome and were cotransducible. Induction studies revealed that the three alpha-d-galactosides, melibiose, melibiitol, and galactinol, induced alpha-galactosidase and TMG permease II coordinately; d-galactose also induced them but only in a galactokinaseless mutant. These data suggest that alpha-galactosidase and TMG permease II may be components of a common operon.
mesh_terms: D003227:Conjugation, Genetic; D004187:Disaccharides / Q000378:metabolism*; D004790:Enzyme Induction; D004926:Escherichia coli / Q000201:enzymology*; D005696:Galactosidases / Q000378:metabolism*; D005827:Genetics, Microbial; D006027:Glycosides / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000378:metabolism*; D009154:Mutation; D011995:Recombination, Genetic; D014161:Transduction, Genetic
chemical_list: D004187:Disaccharides; D006027:Glycosides; D026901:Membrane Transport Proteins; D005696:Galactosidases