GTPase activating protein (GAP) for RSR1 which is involved in the polarization of yeast and hyphal cells. Directs the site of new daughter cell growth in yeast and hyphal cells. Important for hyphae to maintain linear growth and necessary for hyphal responses to directional cues in the environment (tropisms). Required for correct localization of the septin rings and stabilization of the polarisome at hyphal tips. Involved in cell adhesion. Enriched just behind the apices of hyphal tips, appearing as a faint ring at the membrane with a relatively reduced intensity at the extreme tip. Also enriched in the concave angle of some curved hyphae and shows discrete localization to septa. Expression is increased in low iron conditions.