title: Mutations in the lacY gene of Escherichia coli define functional organization of lactose permease.
abstract: Mutations in the lacY gene of Escherichia coli have been used to analyze the functional organization of lactose permease. Deletions suggest that the NH2 terminus of lactose permease is not essential and can be replaced by residues of the cytoplasmic enzyme beta-galactosidase. Negative dominant mutations in the lacY gene can be explained by the assumption that membrane-associated lactose permease is active as a dimer or oligomer. The map positions of these mutations and other point mutations that lower or alter the sugar specificity define regions of lactose permease involved in sugar or proton binding and transport.
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites; D001693:Biological Transport, Active; D002872:Chromosome Deletion; D004926:Escherichia coli / Q000235:genetics; D029968:Escherichia coli Proteins; D007763:Lac Operon; D026901:Membrane Transport Proteins / Q000235:genetics*; D009004:Monosaccharide Transport Proteins; D009154:Mutation; D011522:Protons; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D027981:Symporters
chemical_list: D029968:Escherichia coli Proteins; C050221:LacY protein, E coli; D026901:Membrane Transport Proteins; D009004:Monosaccharide Transport Proteins; D011522:Protons; D027981:Symporters; C021499:lactose permease