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GTPase-activating proteins (GAPs) are a family of regulatory proteins whose primary function is to accelerate the GTPase activity of small GTPases. They are crucial components of the intracellular signaling network.

Function

GAPs function by increasing the rate at which GTP is hydrolyzed to GDP, thus turning off the GTPase. This is important because many small GTPases act as binary switches in intracellular signaling pathways. When bound to GTP, they are in the 'on' state and can interact with downstream effector proteins to propagate signals within the cell. When bound to GDP, they are in the 'off' state and are unable to interact with these effectors.

Types of GTPase-activating proteins

There are many different types of GAPs, each of which interacts with a specific set of GTPases. Some of the most well-studied include the RasGAPs, which interact with the Ras family of GTPases, and the RhoGAPs, which interact with the Rho family of GTPases.

Role in disease

Mutations in GAPs or in their target GTPases can lead to a variety of diseases. For example, mutations in the RasGAP neurofibromin 1 are responsible for Neurofibromatosis type I, a genetic disorder characterized by the growth of tumors along nerves. Similarly, mutations in various RhoGAPs have been implicated in cancer and in neurological disorders such as mental retardation.

See also

• Guanine nucleotide exchange factor
• GTPase
• Ras superfamily

References

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