Gi alpha subunit

G_i alpha subunit (G_αi, or G_i/G₀ or G_i protein) is a heterotrimeric G protein subunit that inhibits the production of cAMP from ATP. A mnemonic for remembering this subunit is to look at first letter (G_αi = Adenylate Cyclase inhibitor).

Receptors

The following G protein-coupled receptors couple to the G_i subunit:

Function

G_i mainly inhibits the cAMP dependent pathway by inhibiting adenylate cyclase activity, decreasing the production of cAMP from ATP, which, in turn, results in decreased activity of cAMP-dependent protein kinase. Therefore, the ultimate effect of G_i is the opposite of cAMP-dependent protein kinase.

Alpha subunit

Alpha subunits (α) refers to several protein subunits, e.g.: