GTPGDP

GTPGDP is a term sometimes used in biochemistry and molecular biology to describe the interconversion between guanosine triphosphate (GTP) and guanosine diphosphate (GDP) within cellular processes. It is not the name of a single chemical entity, but a shorthand for the GTP–GDP cycle that governs the activity of many guanine nucleotide–binding proteins.

In most molecular switches, a GTPase binds GTP to assume an active state. Hydrolysis of GTP to GDP (often releasing inorganic phosphate) converts the protein to an inactive form. The exchange of GDP for GTP, often catalyzed by guanine nucleotide exchange factors (GEFs), reactivates the protein. The GTPGDP cycle thus coordinates timing and localization of signaling events.

GTPases are involved in processes like vesicle trafficking, cytoskeletal dynamics, cell growth, and translation. The cellular energy status, reflected in the GTP/GDP ratio, can influence the rate of nucleotide exchange and hydrolysis, thereby modulating pathway activity.

The phrase GTPGDP is not widely used as a formal term for a specific molecule; in most contexts, scientists refer to the GTP–GDP cycle, the GTPase cycle, or the GTP/GDP ratio. Some literature may use the combined term when discussing nucleotide dynamics in a model or when contrasting GTP-bound and GDP-bound states.

See also: GTPase, GTPase cycle, GDP, GTP, Guanine nucleotide exchange factor, GTPase-activating protein.