Abstract
Plants have two types of H+-pyrophosphatase (H+-PPase). The type I localizes on vacuolar membranes. Type II H+-PPase is different from the type I enzyme in primary sequence and intracellular localization. Previous work using GFP-fusion protein revealed the Golgi apparatus localization of type II H+-PPase (FEBS Lett. 2001). In this study, we aim to determine actual localization of endogenous type II of Arabidopsis (AtVHP2;1) and absolute protein amount. The level of AtVHP2;1 was quantified in several organs at different growth stages by immunoblotting. For suspension cultured cells, the content of AtVHP2;1 was less than 0.5% of that of type I enzyme. When the intracellular localization was determined by sucrose density gradient centrifugation, AtVHP2;1 was not co-fractionated with RGP1 (marker of trans-Golgi), AtVSR1/AtELP (PVC/TGN marker), or the other markers of the ER, vacuolar, or plasma membranes. With consideration of its small amount in cells, AtVHP2;1 may be located to small, minor organelle.
