Roles of basic residues and salt-bridge interaction in a vacuolar H+-pumping pyrophosphatase (AVP1) from Arabidopsis thaliana.

To investigate the possible role of basic residues in H+ translocation through vacuolar-type H+-pumping pyrophosphatases (V-PPases), conserved arginine and lysine residues predicted to reside within or close to transmembrane domains of an Arabidopsis thaliana V-PPase (AVP1) were subjected to site-directed mutagenesis. One of these mutants (K461A) exhibited a "decoupled" phenotype in which proton-pumping but not hydrolysis was inhibited. Similar results were reported previously for an E427Q mutant, resulting in the proposal that E427 might be involved in proton translocation.