title: cys154 Is important for lac permease activity in Escherichia coli.
abstract: The lac Y gene of Escherichia coli which encodes the lac permease has been modified by oligonucleotide-directed, site-specific mutagenesis such that cys154 is replaced with either gly or ser. Permease with gly in place of cys154 exhibits essentially no transport activity, while substitution of cys154 with ser also causes marked, though less complete loss of activity. The findings suggest that cys154 plays an important role in lactose:H+ symport.
mesh_terms: D001483:Base Sequence; D001692:Biological Transport; D003545:Cysteine / Q000235:genetics; D004262:DNA Restriction Enzymes / Q000378:metabolism; D015246:Deoxyribonuclease EcoRI; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*; D029968:Escherichia coli Proteins; D007785:Lactose / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000378:metabolism*; D009004:Monosaccharide Transport Proteins; D009154:Mutation; D009693:Nucleic Acid Hybridization; D027981:Symporters
chemical_list: D029968:Escherichia coli Proteins; C050221:LacY protein, E coli; D026901:Membrane Transport Proteins; D009004:Monosaccharide Transport Proteins; D027981:Symporters; C021499:lactose permease; D004262:DNA Restriction Enzymes; D015246:Deoxyribonuclease EcoRI; D007785:Lactose; D003545:Cysteine