You are interested in examining the regulation of the gene that encodes an enzym
ID: 91407 • Letter: Y
Question
You are interested in examining the regulation of the gene that encodes an enzyme, Tre-ase, important in metabolizing trehalose into glucose in bacteria. Trehalose is a disaccharide formed of two glucose units. It is known that two DNA-binding proteins, TreA and TreB, are important for binding to the promoter of the Tre-ase gene and are involved in regulating the transcription of the Tre-ase gene: TreA binds to the "A" site in the promoter region, and TreB binds to the "B" site. You make mutations in the TreA and TreB genes to create cells lacking these genes, observe what happens to transcription of the Tre-ase gene, and obtain the results in Table Q8-16. A. What is the role for TreA in controlling Tre-ase expression? Explain. B. What is the role for TreB in controlling Tre-ase expression? Explain. C. From these data, what do you predict will happen to Tre-ase transcription (compared with that in normal cells) in the presence of trehalose if you were to create a version of the TreA protein that will constitutively bind to the "A" site in the Tre-ase promoter?Explanation / Answer
Answer:
Based on the given information:
When only glucose is present: Glucose is the preferable energy source for bacteria. Therefore in the presence of glucose their is no need for bacteria to metabolize Trehalose. Since the Trease enzyme is regulated, therefore cells do not produce this enzyme in the presence of glucose. This is achieved by TreA binding to the promoter region and inhibiting the transcription of Trease enzyme. Trehalose positively regulates the expression, and in normal cells whenever this molecule is present (without the presence of glucose) the Tre-ase enzyme will be transcribed.
A) What is the role of TreA in controlling the expression of Tre-ase enzyme?
As explained above, in normal cells, when glucose is present, TreA plays a role of repressor and inhibits the Trease transcription in the absence of trehalose.
B) What is the role of TreB in controlling the expression of Tre-ase enzyme?
Since cells that lack TreB are unable to produce Tre-ase enzyme whenever trehalose is present, it indicates that TreB gene synthesizes activator for Tre-ase gene trascription. In the absence of this gene product, Tre-ase is not synthesize even if trehalose is present.
C) What will happen to Tre-ase transcription, in the presence of trehalose if you were to create a version of the TreA protein that will constitutively bind to the "A" site in the Tre-ase promoter?
Since Tre-A protein acts as an repressor, therefore, if it is constitutively expressed and binds to the A site in the Tre-ase promoter it will
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