BIO 226L Lecture Notes - Lecture 8: Lactose Permease, Lac Repressor, Tetrameric Protein

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orangemammoth579

27 Jan 2020

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10/28 - quiz 4 - lecture 8: lac operon & -galactosidase assay. Takes in lactose (lactose permease channel - membrane protein) -galactosidase metabolizes it to galactose galactose metabolism glycolytic pathway & glucose glycolytic pathway. Lac operon = polycistronic lac message - multiple genes on the same rna and are translated to make different proteins. Promoter, lacz, lacy, laca lacz = -galactosidase: breaks down lactose lacy = lactose permease laca = galactoside acetylase. Repressor (tetrameric) - produced from the lac gene product. Binds to operator sequences - tie the dna in an anti-transcriptional knot so rna polymerase can"t initiate transcription from that spot. Still have basal level of transcription of the lac operon - low concentrations on the gene products. Beta- gal second activity: metabolize lactose allo-lactose (inducer) Binds to subunits fo lac repressor to inactivate it. Rate of synthesis of beta-gal & lactose in medium over time.

Related Questions

In the following points, I have summarized Lac operon in Ecoli. I need to check if this is on the right track? and where does 'cleavage of disaccharides' fit into this picture?

Lactose is a disaccharide and the bacteria need specific genes to manage catabolism

1) The lacl promotor gene synthesis the repressor protein which binds to the operator gene stopping the RNA polymerase from coding the lac operon genes

2)But when lactose is present, it needs the specific genes to catabolise lactose

3) So, When allolactose (a derivative of lactose)is present, it binds to the repressor protein, the repressor releases from the operator gene

4) This allows the RNA polymerase can attach to the DNA control region

5) And drive down the operon for transcription and induction of the enzyme lacZ(beta-galactosidase) lacY and lacA which breaks lactose down into glucose and galactose

6) When the lactose is all gone, the repressor returns to the operator in a feedback loop system

When (glucose, lactose) ___________ levels inside a bacterial cell are low, cyclicAMP levels are (high, low) __________. This is because metabolizes sugars (activate, inhibit) ___________ the enzyme adenylate cyclase, and (activate, inhibit) __________ the enzyme cAMP phosphodiesterase, causing cyclic AMP levels to rise. Consequently, the CAP protein is (Activated, inhibited, unaffected) ___________ by the cyclic AMP and binds to the lac promoter region, and the CAP protein acts like a sigma factor recruiting (DNA, RNA) ___________ polymerase to the promoter. This establishes condition that may lead to the (transcription, replication) __________ of the lac operon if (allolactose, glucose, lactose) _____________ is available to bind to (lac repressor, lacZ, lacY, lacA) _________ protein keeping this protein from binding to the (lacO, lacZ. lacY, lacA) ___________ gene.

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BIO 226L Lecture Notes - Lecture 8: Lactose Permease, Lac Repressor, Tetrameric Protein

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