Predicted to enable GTPase activator activity. Involved in myosin filament assembly; positive regulation of GTPase activity; and vascular associated smooth muscle contraction. Predicted to be located in endoplasmic reticulum and mitochondrion. Predicted to be active in cytosol. Orthologous to human RAP1GDS1 (Rap1 GTPase-GDP dissociation stimulator 1). [provided by Alliance of Genome Resources, Apr 2022]