Characterization and sequencing of an uncoupled lactose carrier mutant of Escherichia coli.
A lactose carrier mutant of Escherichia coli (ML308-22) showed a severe defect in thiomethylgalactoside accumulation but a faster than normal entry of o-nitrophenyl-galactoside. Sequencing of the mutant lacY gene revealed a point mutation resulting in the substitution of glycine-159 by a cysteine residue. The mutant showed an increased sensitivity to sulfhydryl reagents, a property that is consistent with the view that the Cysteine-159 is in or near the sugar recognition site and the energy coupling region of the carrier.
Matos
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Department of Cell Biology, Harvard Medical School, Boston, MA 02115.
Wilson
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D000595:Amino Acid Sequence; D001483:Base Sequence; D001692:Biological Transport; D017931:DNA Primers; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins; D005798:Genes, Bacterial; D007700:Kinetics; D007785:Lactose / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D008756:Methylgalactosides / Q000378:metabolism; D008961:Models, Structural; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins; D009154:Mutation; D016133:Polymerase Chain Reaction; D017433:Protein Structure, Secondary; D027981:Symporters; D013816:Thermodynamics; D013862:Thiogalactosides / Q000378:metabolism
D017931:DNA Primers; D029968:Escherichia coli Proteins; C050221:LacY protein, E coli; D026901:Membrane Transport Proteins; D008756:Methylgalactosides; D009004:Monosaccharide Transport Proteins; D027981:Symporters; D013862:Thiogalactosides; C009468:thiomethylgalactoside; C021499:lactose permease; D007785:Lactose