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 is 1 gene for this protein in each of the chloroplast inverted repeats; while they are usually identical, in this organism they are not. The other copy is AC A4QKZ7.