GTPaseaktivierende

GTPaseaktivierende Proteine, often abbreviated as GAPs, are a class of proteins that regulate the activity of small GTPases. Small GTPases are molecular switches that cycle between an inactive GDP-bound state and an active GTP-bound state. This cycling is crucial for a wide range of cellular processes, including cell growth, differentiation, and intracellular trafficking.

GAPs function by increasing the intrinsic rate of GTP hydrolysis by the small GTPase. When a GAP binds to a small GTPase that is in its active GTP-bound state, it facilitates the conversion of GTP to GDP. This process effectively turns off the GTPase, returning it to its inactive state. The interaction typically involves a conserved arginine residue in the GAP that inserts into the nucleotide-binding pocket of the GTPase, stabilizing the transition state for hydrolysis.

The activity of GAPs is critical for maintaining proper signaling. Dysregulation of GAP activity can lead to uncontrolled activation of small GTPases, contributing to various diseases, including cancer and developmental disorders. Conversely, some other proteins, known as Guanine nucleotide Exchange Factors (GEFs), promote the activation of small GTPases by facilitating the release of GDP and the binding of GTP. The balance between GAP and GEF activity is therefore essential for precise control of cellular functions regulated by small GTPases.