GTPase-activating protein for Rho family members. May interact with RASA1/p120GAP. Also membrane-associated in a fibrillar pattern that colocalizes with the alpha5-beta1 integrin receptor (ITGA5/ITGB1) for fibronectin. Expressed in spinal cord, cerebellum, kidney, testis and lung. The pG1 pseudoGTPase domain does not bind GTP.