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. Detected polypeptides range in size from 130 to 180 kDa; it is not clear which parts of the protein are stably expressed. Polymorphisms exist between different plastome types; no difference is detected in the protein's molecular weight in polyacrylamide gels, but these changes are seen by isoelectric focusing. Belongs to the Ycf2 family.