Neurofibromin is the product of the neurofibromatosis type 1 gene (NF1) and shares a region of similarity with catalytic domain of the mammalian p120RasGAP protein and an extended similarity with the Saccharomyces cerevisiae RasGAP proteins Ira1 and Ira2. Neurofibromin has been shown to function as a GAP (GTPase-activating protein) which inhibits low molecular weight G proteins such as Ras by stimulating their intrinsic GTPase activity. NF1 is a common genetic disorder characterized by various symptoms ranging from predisposition for the development of tumors to learning disability or mental retardation. Loss of neurofibromin activity can be correlated to the increase in Ras-GTP concentration in neurofibromas of NF1 of patients, supporting the notion that unregulated Ras signaling may contribute to their development.
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