G-protein
G-protein
G-protein (pronounced: gee-proh-teen) is a type of protein that acts as a molecular switch inside cells. It is involved in transmitting signals from a variety of stimuli outside a cell to its interior.
Etymology
The term "G-protein" is derived from the fact that these proteins bind to guanine nucleotides. The "G" stands for guanine, a component of both GDP (guanosine diphosphate) and GTP (guanosine triphosphate), which are molecules that G-proteins bind to and hydrolyze.
Function
G-proteins are a family of proteins involved in second messenger systems. They are activated by G-protein-coupled receptors (GPCRs) that are located on the cell surface and respond to different stimuli. When a ligand binds to a GPCR, it causes a conformational change in the receptor, which allows it to act as a guanine nucleotide exchange factor (GEF). The GPCR can then activate an associated G-protein by exchanging the GDP bound to the G-protein for a GTP.
Types
There are several types of G-proteins, including G_s, G_i, G_q, and G_12/13. Each type has a different effect on the cell. For example, G_s stimulates the production of cyclic AMP (cAMP), while G_i inhibits it. G_q stimulates the phospholipase C pathway, and G_12/13 are involved in Rho family GTPase signaling.
Related Terms
- G-protein-coupled receptor (GPCR)
- Guanine nucleotide exchange factor (GEF)
- Cyclic AMP (cAMP)
- Phospholipase C (PLC)
- Rho family of GTPases
External links
- Medical encyclopedia article on G-protein
- Wikipedia's article - G-protein
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