EGTA is a Ca2 chelator meaning that EGTA binds very strongly

EGTA is a Ca^2+ chelator meaning that EGTA binds very strongly to Ca^2+ and prevents free Ca^2+ in the cell. Predict the result of adding EGTA to a G-protein signal system that activates CREB binding protein.

Solution

Answer:

Receptor stimulation leads to the activation of adenylate cyclase with the help of G-proteins. Activated adenylate cyclase forms cAMP which inturn activates protein kinase A. Activated PK-A is then translocated to nucleus through nucleus pore. These activated PK-A, phosphorylates the transcription factor Ca²⁺/cAMP response element binding protein (CREB).

Once phosphorylated, CREB forms a dimer via a conserved heptad repeat of leucine residues at the C-terminus then associates with CREB binding protein, which recruits and stabilizes RNA polymerase II, forming a transcription complex at the cAMP response element (CRE), an 8-bp motif 5-TGACGTCA-3.

If we make it very simple, GPCR pathway of CREB activation involves cAMP. CREB activation by Ca²⁺ is a complete different pathway. So, addition of EGTA should not inhibit GPCR signaling system that activates CREB binding protein.