Escherichia coli lactose operon

Gamer, M. M., and Revzin, A. (1981). A gel electrophoresis method for quantifying the binding of proteins to specific DNA regions Application to components of the Escherichia coli lactose operon regulatory system. Nucleic Acids Res. 9, 3047—3060. 

Gamer, M.M., Revzin, A. (1981) A Gel Electrophoresis Method for Quantifying the Binding of Proteins to Specific DNA Regions Applications to Components of the Escherichia coli Lactose Operon Regulatory System, Nucleic Acids Res. 9, 3047-3060. 

Mellon, I. and Hanawalt, P.C. (1989) Induction of the Escherichia coli lactose operon selectively increases repair of its transcribed DNA strand. Nature, 342, 95-98. 

More than 30 years ago Jacob and Monod introduced the Escherichia coli lac operon as a model for gene regulation. The lac repressor molecule functions as a switch, regulated by inducer molecules, which controls the synthesis of enzymes necessary for E. coli to use lactose as an energy source. In the absence of lactose the repressor binds tightly to the operator DNA preventing the synthesis of these enzymes. Conversely when lactose is present, the repressor dissociates from the operator, allowing transcription of the operon. 

The control and expression of protein in eukaryotic cells is more complex than in bacteria. Research into this field is ongoing and, as such, is beyond the scope of this text. Many systems of control are known in bacteria and can be used to illustrate the type of control mechanisms and the importance of the environmental control of protein synthesis. The first and best documented example is that of the lactose (lac) operon is Escherichia coli. 

The regulation of bacterial transcription is well illustrated by the lactose operon (lac operon) of the colon bacterium Escherichia coli in which the upstream region successively (from the 5 end of the sense strand) includes a promoter (P ) for the gene (I) coding for a repressor protein (the lac repressor), a CRP binding site , the promoter for the lac operon (P), and finally an operator site (O) that prefaces the Z, Y and A structural genes of the operon ... 

Which of the following best describes the negatively controlled lactose operon in Escherichia coli ... 

Brabetz, W., Liebl, W., and Schleifer, K.H. (1991) Studies on the utilization of lactose by Corynebacterium glutamicum, bearing the lactose operon of Escherichia coli. Arch. Microbiol., 155 (6), 607-612. 

To investigate the importance of this type of regulation of solute transport for other (non-phototrophic) bacteria, Rps. sphaeroides was provided with the ability to transport lactose via transformation with a plasmid containing the lactose operon from Escherichia coli and subsequent expression of the plasmid DNA with the aid of the antibiotic kanamycine (F.E. Nano, S. Kaplan, unpublished). The initial rate of lactose transport in Rps. sphaeroides was studied as a function of the light intensity and the magnitude of the proton motive force. 

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