Inhibits the Ras signaling pathway through its intrinsic Ras GTPase-activating protein (GAP) activity. Acts as a negative feedback inhibitor of the calcineurin signaling pathway that also mediates crosstalk between calcineurin and Ras. Interacts with both calcineurin and HRAS. Most abundant in spleen and peripheral blood leukocytes. The arginine and glutamine fingers are critical for the GTPase-activating mechanism, they pull out Rab's 'switch 2' glutamine and insert in Rab's active site.