Predicted to enable ATPase activator activity. Involved in vacuolar proton-transporting V-type ATPase complex assembly. Part of vacuolar proton-transporting V-type ATPase complex. Is expressed in several structures, including adult head; adult heart; embryonic/larval midgut primordium; larval muscle system; and midgut. Human ortholog(s) of this gene implicated in immunodeficiency 47. Orthologous to several human genes including ATP6AP1 (ATPase H+ transporting accessory protein 1).