How many subunits are there in a G protein?

A G protein, which is involved in transmitting signals from various stimuli outside a cell to its interior, is composed of three distinct subunits: alpha, beta, and gamma. Each of these subunits plays a specific role in the signaling process.

The alpha subunit binds to guanine nucleotides (GDP and GTP), which are vital for the activation and inactivation of the G protein. When a ligand binds to a receptor, it causes the alpha subunit to exchange GDP for GTP, leading to the activation of the G protein. The beta and gamma subunits act as a dimer, remaining associated with each other and influencing various downstream signaling pathways.

The presence of these three subunits is essential for the proper functioning and regulation of the G protein signaling pathways. Thus, the configuration of three subunits in G proteins is crucial for their role in cell signaling.