You have discovered a new gene that encodes an unusual regulatory subunit of PKA, which you name Ro. As with the R2C2 version of PKA, Ro forms a dimer and interacts with two molecules of the same catalytic subunit (C) found in PKA to form a Ro2C2 heterotetramer. However, unlike the R in conventional PKA, each Ro subunit binds 8 molecules of cAMP. Which of the following properties would you predict Ro2C2 PKA would display compared to the conventional R2C2 form of PKA?A. PKA with Ro subunits would become active at a lower concentration of cAMP. B. Full activity of PKA with Ro subunits would occur at a higher concentration of cAMP. C. The dynamic range of activity of PKA with Ro subunits would occur over a narrower range of cAMP concentration. D. The dynamic range of activity of PKA with Ro subunits would over a wider range of cAMP concentration.

The answer is B and D.

Explanation:

PKA ( Protein Kinase A) is an enzyme which becomes active with the presence of cAMP molecules in the cell and the cAMP molecules need to bind to R subunits to become active which happens at a ratio of 1:2.

The example given in the question states that the Ro sububit can bind to 8 molecules of cAMP rather than the conventional 2.

This means that the activation of the Ro subunits is harder than the activation of R subunit because of the requirement of higher cAMP concentrations.

B is correct, full activity of PKA with Ro subunits needs a higher concentration of cAMP.

Because Ro binds to eight units of cAMP, the dynamic range of activity of PKA with Ro is going to be over a wider range of cAMP concentration.

I hope this answer helps.

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