Multiple choice

In a G protein mediated signal transduction cascade of cAMP, adenylase cyclase is activated by

  1. G-alpha GDP complex with G-beta, Gama subunits

  2. G-beta GDP Complex

  3. G-alpha-beta GDP complex

  4. G-beta-gama GDP complex

  5. G-alpha GTP complex
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

GTP in addition to the G protein is essential for the signal transduction to proceed. G-alpha is the activated subunit of G-protein. The binding of a ligand like epinephrine causes conformational change in the G-protein that assist in making the nucleotide binding site of the G-protein more accessible to the cytosol where the concentration of GTP is high. The alpha unit of it releases the GDP and binds to GTP. In other words, GTP is exchanged for the GDP. The binding of GTP causes additional conformational change in G alpha subunit and then G-protein disassociates to leave beta and Gama units. G alpha-GTP complex then binds to adenylate cyclase and activates it.

Keep practicing — related questions