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Molecular analysis of the lac operon encoding the binding-protein-dependent lactose transport system and β-galactosidase in Agrobacterium radiobacter
Article first published online: 27 OCT 2006
DOI: 10.1111/j.1365-2958.1992.tb01348.x
1365-2958/asset/cover.gif?v=1&s=75254d9e3ae6a0f08085f34cc6e5bd65d8e3d52e "Molecular Microbiology")
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How to Cite
Williams, S. G., Greenwood, J. A. and Jones, C. W. (1992), Molecular analysis of the lac operon encoding the binding-protein-dependent lactose transport system and β-galactosidase in Agrobacterium radiobacter. Molecular Microbiology, 6: 1755–1768. doi: 10.1111/j.1365-2958.1992.tb01348.x
Publication History
- Issue published online: 27 OCT 2006
- Article first published online: 27 OCT 2006
- Received 20 January, 1992; revised and accepted 18 March, 1992.
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Summary
The genes coding for the binding-protein-dependent lactose transport system and β-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 β-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.