lac repressors การใช้

• The lac repressor is a four-part protein, a tetramer, with identical subunits.
• So, he added, " difficult problems like the lac repressor tend to be put aside ."
• The binding of the lac repressor to RNA polymerase's binding site inhibits the transcription of the lac genes.
• Both hybrid promoters can be repressed by the lac repressor and both can be derepressed with isopropyl-beta-D-thiogalactoside.
• This DNA sequence is bound by the lac repressor, which, in turn, prevents transcription of the adjacent genes on the same DNA molecule.
• Only when a corepressor is bound to the lac repressor will the binding site be free for RNA polymerase to carry out transcription of the lac genes.
• In terms of the lac operon, the negative regulator would be the lac repressor which binds to the promoter in the same site that RNA polymerase normally binds.
• The presence of allolactose, a metabolic product of lactose, is sensed through the activity of the lac repressor, which inhibits transcription of the lac operon until lactose is present.
• With his Ph . D . student Benno M黮ler-Hill, Gilbert was the first to purify the lac repressor, just beating out Mark Ptashne for purifying the first gene regulatory protein.
• Lac Repressor ) closer to the DNA to increase their attraction and enable them to bind, as well as steric effect which exclude the Crowder proteins from this region ( Lac operator region ).
• Its production may be induced by a non-hydrolyzable analog of allolactose, IPTG, which binds and releases the lac repressor from the lac operator, thereby allowing the initiation of transcription to proceed.
• Like allolactose, IPTG binds to the lac repressor and releases the tetrameric repressor from the lac operator in an allosteric manner, thereby allowing the transcription of genes in the lac operon, such as the gene coding for beta-galactosidase, a hydrolase enzyme that catalyzes the hydrolysis of ?-galactosides into monosaccharides.
• This repressor ( the lac repressor ) is made in all cells, binding directly to DNA at the genes it controls, and physically preventing the transcription apparatus from gaining access to the DNA . In the presence of lactose, this repressor binds lactose, making it no longer able to bind to DNA, and the transcriptional repression is lifted.