Abstract
Previous investigation in our laboratory demonstrated thatmodification of tonoplast vesicles and purified vacuolar H+-PPase from etiolated mung bean seedlings with tetranitromethaneresulted in a progressive decline in H+-translocatingpyrophosphatase activity. The authors suggested that tyrosineresidues, especially Tyr627, of V-PPase from mung beanseedlings may be important for enzyme activity. For furtherverification, we mutated all 12 cytosolic tyrosine residues bysite-directed mutagenesis to study the active site(s) of V-PPasefrom mung bean seedlings. In this study, the pYES2-VVP was usedto transform yeast strain INVSC2 and expressed the functionalenzymes. The heterologously expressed V-PPase are different fromyeast soluble PPase. Thereby, the 12 mutants could be evaluatedin this system.