GTP exchange factors

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GEF and GAP system.jpg

A GTP exchange factor ( Guanosine triphosphate exchange factor , GEF) is a signal protein that acts on a G protein in such a way that it exchanges a bound GDP for a GTP . In most cases, the G-protein is activated and acts on various effectors . The antagonists of the GTP exchange factors are the GTPase- activating proteins ( GAP ) which activate the GTPase activity of the G-protein (which causes it to hydrolyze the bound GTP to GDP by splitting off a phosphate residue ). The GTP exchange factors play an important role in many biochemical processes, since without them there would be no activity of the G proteins. These in turn play a decisive role in a large number of signal transduction pathways. Examples of G proteins that need a GTP exchange factor to function are proteins of the Ras family , all heterotrimeric G proteins such as G s , G i , G q and Golf . About 150 GTP exchange factors are known in humans.


  • Bruce Alberts et al .: Molecular Biology of the Cell. 4th edition. Garland Science, New York, NY 2002, ISBN 0-815-33218-1 .