G-proteins

Guanine nucleotide binding protein that binds GTP when activated, which it hydrolyses to GDP.  The active form of the protein can interact with a number of down stream effectors such as adenylyl cyclase (producing cAMP from ATP), and phospholipase C (PLC).

The G-proteins can be divided in to two families - the heterotrimeric G-proteins and the small or mono-meric G-proteins.

G Proteins consist of 3 sub units ; an alpha, a beta and a gamma. There are 4 familys of alpha subunit : s,q,i and 12. In addition the beta and gamma subunits combine to form a dimer which also serves as a functional unit.