title: Molecular analysis of the lac operon encoding the binding-protein-dependent lactose transport system and beta-galactosidase in Agrobacterium radiobacter.
abstract: The genes coding for the binding-protein-dependent lactose transport system and beta-galactosidase in Agrobacterium radiobacter strain AR50 were cloned and partially sequenced. A novel lac operon was identified which contains genes coding for a lactose-binding protein (lacE), two integral membrane proteins (lacF and lacG), an ATP-binding protein (lacK) and beta-galactosidase (lacZ). The operon is transcribed in the order lacEFGZK. The operon is controlled by an upstream regulatory region containing putative -35 and -10 promoter sites, an operator site, a CRP-binding site probably mediating catabolite repression by glucose and galactose, and a regulatory gene (lacl) encoding a repressor protein which mediates induction by lactose and other galactosides in wild-type A. radiobacter (but not in strain AR50, thus allowing constitutive expression of the lac operon). The derived amino acid sequences of the gene products indicate marked similarities with other binding-protein-dependent transport systems in bacteria.
authors.affiliation: Department of Biochemistry, University of Leicester, UK.
authors.forename: S G
authors.initials: SG
authors.lastname: Williams
authors.forename: J A
authors.initials: JA
authors.lastname: Greenwood
authors.forename: C W
authors.initials: CW
authors.lastname: Jones
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D001692:Biological Transport; D002352:Carrier Proteins / Q000235:genetics*; D003001:Cloning, Molecular; D029968:Escherichia coli Proteins; D005798:Genes, Bacterial; D005809:Genes, Regulator; D007763:Lac Operon; D007785:Lactose / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins; D012231:Rhizobium / Q000235:genetics* / Q000378:metabolism; D027981:Symporters; D001616:beta-Galactosidase / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; C050221:LacY protein, E coli; D008565:Membrane Proteins; D009004:Monosaccharide Transport Proteins; D027981:Symporters; D001616:beta-Galactosidase; D007785:Lactose