Abstract
Plant cell contains vacuolar H+-pyrophosphatase (EC 3.6.1.1), which catalyzes PPi hydrolysis and electrogenic translocation of proton from the cytosol to vacuole lumen. C-terminus deletion of plant V-PPase, showed different degree of decreases in specific activity and proton translocation. The expressed V-PPase of C-terminus deleted, ΔC-69 (truncate 69 amino acids about 7 kDa) particularly lose the enzymatic reaction and proton translocation, but the short fragment deleted mutantΔC-25 was remained the enzymatic ability. C-terminal deletion of V-PPase causes a release of the stimulation of enzymatic activity by KCl and inhibition by Ca2+. The truncated V-PPase longer than lost 25 amino acid lost most of K+ stimulatory and Ca2+ inhibitory effects. The C-terminus of V-PPase may contain K+ and Ca2+ binding domain. Western blot analysis and immunoflouresence microscope indicated that the C-terminal region of V-PPase is involved in protein targeting. Hence, we speculate that the C-terminus of V-PPase may play an essential role in regulating enzymatic activity and stabilizing the enzyme structure.