title: Constitutive activity of Sauromatum guttatum alternative oxidase in Schizosaccharomyces pombe implicates residues in addition to conserved cysteines in alpha-keto acid activation.
abstract: Activity of the plant mitochondrial alternative oxidase (AOX) can be regulated by organic acids, notably pyruvate. To date, only two well-conserved cysteine residues have been implicated in this process. We report the functional expression of two AOX isozymes (Sauromatum guttatum Sg-AOX and Arabidopsis thaliana At-AOX1a) in Schizosaccharomyces pombe. Comparison of the response of these two isozymes to pyruvate in isolated yeast mitochondria and disrupted mitochondrial membranes reveals that in contrast to At-AOX1a, Sg-AOX activity is insensitive to pyruvate and appears to be in a constitutively active state. As both of these isozymes conserve the two cysteines, we propose that such contrasting behaviour must be a direct result of differences in their amino acid sequence and have subsequently identified novel candidate residues.
authors.affiliation: Department of Biochemistry, School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9QG, UK.
authors.forename: Paul G
authors.initials: PG
authors.lastname: Crichton
authors.forename: Charles
authors.initials: C
authors.lastname: Affourtit
authors.forename: Mary S
authors.initials: MS
authors.lastname: Albury
authors.forename: Jane E
authors.initials: JE
authors.lastname: Carré
authors.forename: Anthony L
authors.initials: AL
authors.lastname: Moore
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics; D029064:Araceae / Q000201:enzymology* / Q000235:genetics; D019295:Computational Biology; D017124:Conserved Sequence; D003545:Cysteine / Q000737:chemistry; D004789:Enzyme Activation; D007425:Intracellular Membranes / Q000201:enzymology; D008928:Mitochondria / Q000201:enzymology; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry* / Q000378:metabolism*; D010940:Plant Proteins; D011487:Protein Conformation; D019289:Pyruvic Acid / Q000494:pharmacology*; D012568:Schizosaccharomyces / Q000201:enzymology* / Q000235:genetics; D025801:Ubiquitin / Q000378:metabolism; D000099188:Alternative Oxidase
chemical_list: D003545:Cysteine; D024101:Mitochondrial Proteins; D010088:Oxidoreductases; D010940:Plant Proteins; D019289:Pyruvic Acid; D025801:Ubiquitin; D000099188:Alternative Oxidase