G-protein

Definition

G-proteins are guanine nucleotide-binding proteins that act as molecular switches inside cells, involved in transmitting signals from various stimuli outside the cell to its interior. They play a crucial role in activating or inhibiting downstream signaling pathways in response to hormone binding to cell surface receptors.

5 Must Know Facts For Your Next Test

1. G-proteins are activated by G-protein-coupled receptors (GPCRs) when a hormone binds to these receptors.
2. They consist of three subunits: alpha, beta, and gamma.
3. The alpha subunit binds GDP in its inactive state and GTP when activated.
4. Upon activation, the G-protein can influence various intracellular signaling pathways such as adenylate cyclase or phospholipase C.
5. Deactivation occurs when the alpha subunit hydrolyzes GTP to GDP, reassociating with the beta and gamma subunits.

Review Questions

Related terms

G-protein-coupled receptor (GPCR): GPCRs are a large family of cell surface receptors that respond to various external signals by activating G-proteins.

Adenylate Cyclase: An enzyme that converts ATP to cyclic AMP (cAMP) upon activation by certain G-proteins.

Phospholipase C: An enzyme activated by some G-proteins that cleaves phospholipids into secondary messengers like IP3 and DAG.