What was the eventual hypothesis proposed bythe researchers to explain the function of the lacI gene and theregulation of the lac operon?

The figure at the beginning of this chapter showsthe binding of both a Lac repressor tetramer and aCRP-cAMP complex to the regulatory region of thelac operon.a. What is the key feature of a regulatory protein suchas the Lac repressor or CRP that allows it to regulate specifically the genes or operons it is supposedto control?b. On the figure, show the positions of the followingcomponents: (i) A Lac repressor monomer; (ii) a Lacrepressor dimer; (iii) all four DNA binding domains ofthe Lac repressor tetramer; (iv) a single helix-turnhelix motif; (v) the o1 part and either the o2 or o3 partsof the lac operator (assume the operon would be transcribed from right to left on the figure); (vi) themultimerization domains of the four Lac repressormonomers; (vii) an inducer-interacting domain; (viii)the CRP-cAMP complex; and (ix) a DNA loop.c. What is the physical basis for the formation of theDNA loop shown in the figure?d. On the figure, show the position of two axes ofsymmetry in the sequence…

With respect to the lac operon, what is allolactose?

What properties demonstrate that the lac repressor is a protein?Describe the evidence that it indeed serves as a repressor withinthe operon system.

The activator (V protein) that is present in the bacterial cell is normally phosphorylated, but only binds to the A site in the operon when it is not phosphorylated. What operon-independent mechanism can regulate the binding of (and also ultimately regulates the removal of) protein V to the A site? Describe this binding/removal mechanism in detail – useappropriateterminologythatwasdiscussedinlecture. Aspartofyouransweraboutthisactivatorproteinbindingto (and then detaching from) the A site of the operon, be sure to address what are the results of this type of control in terms of function of the operon.

The lac operon consisting of lacl, lacZ and lacY genes in addition to all the transcripton factors is used to modulate the level of lactose in the cell. Please describe the cycle of fluctuations in lactose levels and why they occur by referencing the specific components. If glucose is a byproduct of this process, how are the glucose levels in relation to the lactose level fluctuations and the reason for those fluctuations?