Identification and purification of substrate-binding subunit of higher plant H super(+) -translocating inorganic pyrophosphatase

The H super(+) -translocating inorganic pyrophosphatase (H super(+) -PPase) of Beta) vacuolar membrane (tonoplast) vesicles has been purified by 90-fold from detergent-solubilized membranes and the MgPP sub(i)-binding subunit identified by affinity labeling. The purified enzyme has a specific activity of 1100 mu mol/mg multiplied by h and contains one prevalent M sub(r) = 64000 polypeptide which strictly copurifies with activity. It is deduced that the M sub(r) = 64000 polypeptide constitutes the MgPP sub(i) -binding subunit of the H super(+)-PPase.