Question

What are the proteins used to transport information after the first activation of the ligand Adrenaline/epinephrine?

And what is the destined protein? where is it placed in the cell?

Answer 1

cAMP carries the information after the first activation of the ligand. G proteins along with other downstream components are involved in this early signaling cascade when epinephrine binds to the cell surface receptor.

The G protein binds to the activated receptor, releases GDP, and takes up a molecule of GTP. The G protein activates an enzyme called adenylyl cyclase, adenylyl cyclase then converts a large number of ATP molecules into signaling molecules, called cyclic AMP (cAMP). Because cAMP carries the message of the first messenger (epinephrine) into the cell, cAMP is referred to as a second messenger.

This ultimately leads to the phosphorylation cascade and phosphorylation and activation of Glycogen phosphorylase which, breaks down glycogen into its component glucose molecules. It is present in the cytosol.

and that how involved in the "fight-or-flight" response.