Endoribonuclease which preferentially cleaves ApU and ApG phosphodiester bonds. Hydrolyzes UpU bonds at a lower rate (By similarity). Regulates the activity of vacuolar (H+)-ATPase (V-ATPase) which is responsible for acidifying and maintaining the pH of intracellular compartments (By similarity). Required at an early stage of receptor-mediated endocytosis (By similarity). Interacts with the proton translocation complex V0 of the V-ATPase (By similarity). Interacts with ATP6AP1 (By similarity). Belongs to the RNase K family.