title: Roles of basic residues and salt-bridge interaction in a vacuolar H+-pumping pyrophosphatase (AVP1) from Arabidopsis thaliana.
abstract: 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. However, the double mutant E427K/K461E 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.
authors.affiliation: Biology Department (Area 9), University of York, PO Box 373, York YO10 5YW, UK. marco.zancani@uniud.it
authors.forename: Marco
authors.initials: M
authors.lastname: Zancani
authors.forename: Lorna A
authors.initials: LA
authors.lastname: Skiera
authors.forename: Dale
authors.initials: D
authors.lastname: Sanders
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology*; D029681:Arabidopsis Proteins; D006639:Histidine / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D043564:Inorganic Pyrophosphatase / Q000737:chemistry / Q000502:physiology*; D007700:Kinetics; D008239:Lysine / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017494:Proton Pumps / Q000737:chemistry / Q000502:physiology*; D011522:Protons; D012965:Sodium Chloride / Q000737:chemistry / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D017494:Proton Pumps; D011522:Protons; D012965:Sodium Chloride; D006639:Histidine; C505048:AVP1 protein, Arabidopsis; D043564:Inorganic Pyrophosphatase; D008239:Lysine