Question

Which of the following statements about G-Protein Coupled Receptor (GPCR) signaling or Protein Kinase A (PKA) activation is correct?

I. GPCR kinases phosphorylate GPCRs on their intracellular surface promoting the binding ofβ-Arrestin and the inhibition of GPCR signaling.

II. The pseudosubstrate sequence located in the PKA regulatory domain binds to an AKAP protein in the absence of cAMP.

III. The PKA catalytic and regulatory domains are part of a single polypeptide chain.

IV. The slow hydrolase activity of the PKA regulatory subunit hydrolyzes cAMP which turns off PKA activity.

Choose the best answer

II and III

II, III, and IV

I, II, and III

I only

I and II

Answer 1

the correct option is I and II

the first statement GPCR kinases phosphorylate GPCRs on their intracellular surface promoting the binding ofβ-Arrestin and the inhibition of GPCR signaling is right the binding of a β-Arrestin turns off the phosphorylation of GPCR

the phosphorylation of GPCR require high energy input to save energy cell turn off the receptor by a β-Arrestin

the second statement The pseudosubstrate sequence located in the PKA regulatory domain binds to an AKAP protein in the absence of cAMP. AKAP protein is an A-kinase anchoring protein that has only one function that is to bind to the PKA regulatory domain in the absence of cAMP.

Other options

3rd statement is not true as PKA is a tetramer

the 4th statement is wrong as Gs alpha subunit slowly catalyzes the hydrolyzes GTP to GDP and that causes to turning  off of the Gs protein the given statement is tottaly wrong