GTP-binding protein regulators regulate

G protein G proteins, also known as guanine nucleotide-binding proteins, are a family of proteins that act as molecular switches inside cells, and are involved in transmitting signals from a variety of stimuli outside a cell to its interior. Their a ...

s in several different ways.

Small GTPase Small GTPases (), also known as small G-proteins, are a family of hydrolase enzymes that can bind and hydrolyze guanosine triphosphate (GTP). They are a type of G-protein found in the cytosol that are homologous to the alpha subunit of heterotr ...

s act as molecular switches in signaling pathways, which act to regulate functions of other proteins. They are ''active'' or 'ON' when it is bound to GTP and ''inactive'' or 'OFF' when bound to

GDP Gross domestic product (GDP) is a monetary measure of the market value of all the final goods and services produced and sold (not resold) in a specific time period by countries. Due to its complex and subjective nature this measure is ofte ...

. Activation and deactivation of small GTPases can be regarded as occurring in a cycle, between the GTP-bound and GDP-bound form, regulated by other regulatory proteins.

Exchangers

The inactive form of GTPases (GDP-form) are activated by a class of proteins called Guanosine nucleotide exchange factors (GEFs). GEFs catalyse nucleotide exchange by encouraging the release of GDP from the small GTPase (by displacement of the small GTPase-associated Mg²⁺ ion) and GDP's replacement by GTP (which is in at least a 10-fold excess within the cell) . Inactivation of the active small GTPase is achieved through hydrolysis of the GTP by the small GTPase's intrinsic GTP hydrolytic activity.

Stimulators

The rate of GTP hydrolysis for small GTPases is generally too slow to create physiologically relevant transient signals, and thus requires another class of regulatory proteins to accelerate this activity, the

GTPase activating protein GTPase-activating proteins or GTPase-accelerating proteins (GAPs) are a family of regulatory proteins whose members can bind to activated G proteins and stimulate their GTPase activity, with the result of terminating the signaling event. GAPs are ...

s (GAPs).

Inhibitors

Another class of regulatory proteins, the Guanosine nucleotide dissociation inhibitors (GDIs), bind to the GDP-bound form of Rho and Rab small GTPases and not only prevent exchange (maintaining the small GTPase in an off-state), but also prevent the small GTPase from localizing at the membrane, which is their place of action.

References

External links

* {{GTP-binding protein regulators Proteins