Operon Lactose

Lewis, M., et al. Crystal structure of the lactose operon repressor and its complexes with DNA and inducer. Science 271 1247-1254, 1996. 

Fig. 24.5 Insertion of a cloned insulin gene into a vector carrying a bacterial promoter. The arrow indicates the direction of transcription. If we suppose the bacterial promoter is derived from the lactose operon then transcription will be initiated only in the presence of lactose.

HTHLACI helix turn helix lactose operon repressor B 0(0) 0(0) 1QP0... 

Answer E. TBP and CBP participate in eukaryotic gene transcription and mRNA translation, respectively. CAP regulates the expression of prokaryotic lactose operons. ACP is involved in fatty add synthesis. 

Emulation by activator and repressor proteins in the lactose operon... 

Galactosldase Permease Transacetylase Figure 1-5-1. The Lactose Operon... 

Coordinate Control of the Lactose Operon by Glucose and Lactose... 

Poll expression of the lactose operon requires that both mechanisms favor gene expression. 

A culture of E. colt is grown in a medium containing glucose and lactose. The expression of the lactose operon over time in the cells is shown in the graph below. Which statement best describes the change that occurred at point A ... 

The well-investigated lactose operon of the bacterium Escherichial coli can be used here as an example of transcriptional control. The lac operon is a DNA sequence that is simultaneously subject to negative and positive control. The operon contains the structural genes for three proteins that are required for the utilization of lactose (one transporter and two enzymes), as well as control elements that serve to regulate the operon. 

J.R. Beckwith, D. Zipser, The Lactose Operon Cold Spring Harbor Laboratory, Cold Spring Harbor, 1970, p. 435. 

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 coll lactose operon regulatory system Nucleic Acids Res 9, 3047-3060. 

A variety of different promoters have been used for the expression of antibody genes. Widely used is the lacZ promoter (lacZ) derived from the lactose operon (53). The gill promoter (gill) from the bacteriophage M13 (9), the tetracycline promoter (IX teto/p ref. 54) and the phoA promotor of the E. coli alkaline phosphatase (47) also have been used successfully. It appears that very strong promoters, for example, the synthetic promoter PAI/04/03 (55), are... 

HEK-293 hGH High-Five hsp70 HSV IPTG IRES kb Lac LCR LoxP LUC MCS human embryonic kidney cells human growth hormone TM BTI-TN-5B1-4 (cell line derived from the insect Trichoplusia ni) heat shock protein 70 herpes simplex virus isopropyl 1 -thio-fi-D-galactopyranoside internal ribosomal entry site kilobases lactose operon/repressor locus control region locus of crossover of PI luciferase isolated from firefly multiple cloning site... 

Fig. 4. Selection against the strain of E. coli carrying Tn 10 in the lactose operon in a glucose-limited chemostat.

The end products of gene expression are proteins, mainly enzymes, and it is essential that their levels be strictly controlled. There are many potential sites of control in both bacteria and eukaryotes. DNA or gene amplification (Chap. 16) in eukaryotes is one way of responding to the demand for more of the protein product if there arc more copies of the gene, then transcription can occur at a faster rate. More often, control is effected at the level of cither transcription or translation, with the former probably being more important for both bacteria and eukaryotes. Transcriptional control in bacteria is particularly effective because of the very short half-life (a few minutes) of mRNA in such cells the half-life is longer in eukaryotes. The prototype for transcriptional control is the lactose operon in E. coli. 

Fig. 17-13 The lactose operon of E. coli. Abbreviations i = repressor gene ...

Beckwith, J. R., and Zipser, D., eds. (1970). The Lactose Operon. Cold Spring Harbor, NY Cold Spring Harbor Laboratories. 

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 ... 

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. 

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