Orientation of Pea Stem Mitochondrial H+-Pyrophosphatase and Its Different Characteristics from the Tonoplast Counterpart

Proton pumping pyrophosphatase (H-PP,ase) of pea stem mitochondria appears to be localized on the inner surface of the inner membrane. Aminohexanediphosphonate and dichloromethylenediphosphonate exert different inhibitory effects on this activity and on that of tonoplast. Antibody raised against membrane-bound mitochondrial HPPjase does not react with tonoplast vesicles. Thus, plant mitochondrial H-PPjase seems to have a molecular structure different from that of vacuolar H-PPiase.