Probable ATPase of unknown function. Its presence in a non-photosynthetic plant (Epifagus virginiana) and experiments in tobacco indicate that it has an essential function which is probably not related to photosynthesis. Belongs to the Ycf2 family. There are two genes for this protein in the chloroplast inverted repeat; while they are usually identical, in this organism they are not. The other copy is AC Q8S8V2.