New sequence data enable modelling of the fungal alternative oxidase and explain an absence of regulation by pyruvate.
Respiratory rates involving the alternative oxidase (AO) were studied in mitochondria from Tapesia acuformis. There was no evidence for regulation by pyruvate, in contrast with plant AO. The site of interaction of pyruvate with the plant AO is a conserved cysteine. The primary sequence was obtained for AO from Magnaporthe grisea and compared with four published sequences for fungal AO. In all cases this cysteine was absent. Sequence data were obtained for the C-terminal domain of a further five fungal AOs. In this region the fungal sequences were all consistent with a four-helix, di-iron binding structure as in the ferritin-fold family. A molecular model of this domain was deduced from the structure of Delta-9 desaturase. This is in general agreement with that developed for plant AOs, despite very low sequence identity between the two kingdoms. Further modelling indicated an appropriate active site for binding of ubiquinol, required in the AO redox reaction.
Joseph-Horne
T
T
Department of Biochemistry, School of Medical Sciences, University of Bristol, University Walk, Bristol, UK.
Babij
J
J
Wood
P M
PM
Hollomon
D
D
Sessions
R B
RB
D000595:Amino Acid Sequence; D001665:Binding Sites; D003001:Cloning, Molecular; D017124:Conserved Sequence / Q000235:genetics; D003545:Cysteine / Q000235:genetics / Q000378:metabolism; D019281:Dimerization; D005658:Fungi / Q000201:enzymology* / Q000235:genetics; D020035:Holoenzymes / Q000737:chemistry / Q000378:metabolism; D008928:Mitochondria / Q000201:enzymology* / Q000378:metabolism; D024101:Mitochondrial Proteins; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009243:NAD / Q000378:metabolism; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D010940:Plant Proteins; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D019289:Pyruvic Acid / Q000378:metabolism / Q000494:pharmacology*; D016415:Sequence Alignment; D014451:Ubiquinone / Q000031:analogs & derivatives* / Q000378:metabolism; D000099188:Alternative Oxidase
D003545:Cysteine; D020035:Holoenzymes; D024101:Mitochondrial Proteins; D009243:NAD; D010088:Oxidoreductases; D010100:Oxygen; D010940:Plant Proteins; D019289:Pyruvic Acid; D014451:Ubiquinone; D000099188:Alternative Oxidase; C003741:ubiquinol