Roles of basic residues and salt-bridge pyrophosphatase (AVP1) interaction in a vacuolar H+-pumping 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 transtnembrane domains of an Arabidopsis thaliana V-PPase (AVP1) were subjected to site-directed mutagenesis. One of these mutants (K461 A) 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. However, the double mutant E427K/K461 E has a wild type phenotype, suggesting that E427 and K461 form a stabilising salt bridge, but that neither residue plays a critical role in proton translocation. (c) 2006 Elsevier B.V. All rights reserved.