Common identity of substrate-binding subunit of vacuolar H super(+)-translocating inorganic pyrophosphatase of higher plant cells

There have been conflicting reports in the literature concerning the polypeptide composition of the vacuolar H super(+)-translocating inorganic pyrophosphatase (tonoplast H super(+)-PPase) of plant cells. The major subunit(s) of the enzyme have been attributed to polypeptides of relative molecular weight (M sub(r)) 64,500 (Beta vulgaris)), 67,000 (Beta vulgaris ), 73,000 (Vigna radiata ), and 37,000 to 45,000 (Zea mays ). Here, we reconcile these differences to show, through the combined application of independent purification, affinity-labeling, sequencing, and immunological procedures, that the major polypeptide associated with the H super(+)-PPase from all of these organisms, and Arabidopsis thaliana), corresponds to the same moeity.