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Which of the following is true about the mechanism of relief of autoinhibition of PKA in...

Which of the following is true about the mechanism of relief of autoinhibition of PKA in GPCR signaling?

  1. The zymogen form of the regulatory subunit of PKA is cleaved by proteases, leading to exposure of the binding site of PKA (which binds substrates that it will subsequently phosphorylate).
  2. Phosphorylation of PKA by adenylyl cyclase, which converts cAMP -> AMP.
  3. Binding of cAMP to the regulatory subunit of PKA, which causes a conformational change that releases the regulatory subunit of PKA from the catalytic subunit of PKA (which binds substrates that it will subsequently phosphorylate).
  4. Binding of GTP to the P-loop of the catalytic subunit of PKA.
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Answer #1

The correct answer will be (c) Binding of cAMP to the regulatory subunit of PKA, which causes a conformational change that releases the regulatory subunit of PKA from the catalytic subunit of PKA (which binds substrates that it will subsequently phosphorylate).

Below is a list of the steps involved in PKA activation:

as a result of GPCR pathway ATP-------> cAMP

  1. Cytosolic cAMP increases
  2. Two cAMP molecules bind to each PKA regulatory subunit
  3. The regulatory subunits move out of the active sites of the catalytic subunits and the R2C2 complex dissociates
  4. The free catalytic subunits interact with proteins to phosphorylate Ser or Thr residues.
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