The active site of the cyanide‐resistant oxidase from plant mitochondria contains a binuclear iron center

Siedow, James N.; Umbach, Ann L.; Moore, Anthony L.

doi:10.1016/0014-5793(95)00196-g

Cited by 131 publications

(101 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This result has major implications as to the plausibility of the two structural models. Siedow et al (5,6) implicitly suggested that Glu-217 would be located at the cytoplasmic side of the inner mitochondrial membrane. Since both reduction of oxygen and oxidation of ubiquinol were proposed to occur toward the matrix side of the membrane, it is hard to envisage how Glu-217 would play a functional role in such a model.…”

Section: Discussionmentioning

confidence: 99%

“…Although this second model also classifies the AOX as a di-iron protein, it differs in the precise ligation sphere of the di-iron center (7). For instance, one of the C-terminal Glu-X-X-His motifs identified by Siedow et al (5,6), containing Glu-270, appeared not to be fully conserved in the newly identified sequences and consequently seemed unlikely to play a role in ligating iron. Instead, Andersson and Nordlund used a third Glu-X-X-His motif (that contains Glu-217, which is located in the intermembrane space according to the Siedow et al model) to coordinate the iron atoms.…”

mentioning

confidence: 88%

“…The first model proposed by Siedow et al (5,6) was based on relatively few AOX sequences and classified the AOX as a member of the di-iron family of proteins that also includes the R2 subunit of ribonucleotide reductase and the hydroxylase component of methane monooxygenase. Based on hydropathy analysis, the AOX was predicted to contain two transmembrane helices that are connected by a helix located in the intermembrane space (6) (Fig.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Structure of the Plant Alternative Oxidase

Albury

Affourtit

Crichton

et al. 2002

Journal of Biological Chemistry

Self Cite

View full text Add to dashboard Cite

All higher plants and many fungi contain an alternative oxidase (AOX), which branches from the cytochrome pathway at the level of the quinone pool. In an attempt, first, to distinguish between two proposed structural models of this di-iron protein, and, second, to examine the roles of two highly conserved tyrosine residues, we have expressed an array of site-specific mutants in Schizosaccharomyces pombe. Mitochondrial respiratory analysis reveals that S. pombe cells expressing AOX proteins in which Glu-217 or Glu-270 were mutated, no longer exhibit antimycin-resistant oxygen uptake, indicating that these residues are essential for AOX activity. Although such data corroborate a model that describes the AOX as an interfacial membrane protein, they are not in full agreement with the most recently proposed ligation sphere of its di-iron center. We furthermore show that upon mutation of Tyr-253 and Tyr-275 to phenylalanines, AOX activity is fully maintained or abolished, respectively. These data are discussed in reference to the importance of both residues in the catalytic cycle of the AOX. The alternative oxidase (AOX)1 is a ubiquinol:oxygen oxidoreductase that catalyzes the four electron reduction of oxygen to water (for recent reviews, see Refs. 1-4). This terminal oxidase branches from the cytochrome pathway at the level of the ubiquinone pool and is non-protonmotive. The AOX is resistant to inhibitors of the cytochrome pathway such as cyanide and antimycin A but inhibited by a number of compounds including hydroxamic acids (e.g. salicylhydroxamic acid) and n-alkyl-gallates.Two structural models of the AOX currently exist. The first model proposed by Siedow et al. (5,6) was based on relatively few AOX sequences and classified the AOX as a member of the di-iron family of proteins that also includes the R2 subunit of ribonucleotide reductase and the hydroxylase component of methane monooxygenase. Based on hydropathy analysis, the AOX was predicted to contain two transmembrane helices that are connected by a helix located in the intermembrane space (6) (Fig. 1A). Since this model was proposed, further AOX sequences were identified, resulting in the proposal by Andersson and Nordlund (7) of an alternative structural model (Fig. 1B). Although this second model also classifies the AOX as a di-iron protein, it differs in the precise ligation sphere of the di-iron center (7). For instance, one of the C-terminal Glu-X-X-His motifs identified by Siedow et al. (5,6), containing Glu-270, appeared not to be fully conserved in the newly identified sequences and consequently seemed unlikely to play a role in ligating iron. Instead, Andersson and Nordlund used a third Glu-X-X-His motif (that contains Glu-217, which is located in the intermembrane space according to the Siedow et al. model) to coordinate the iron atoms. Since such a choice implies that the transmembrane helices can no longer be retained, Andersson and Nordlund (7) proposed that the AOX is an interfacial rather than a transmembrane protein.Recently, the IMMUTANS (...

show abstract

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 88%

mentioning

confidence: 99%

See 1 more Smart Citation

Structure of the Plant Alternative Oxidase

Albury

Affourtit

Crichton

et al. 2002

Journal of Biological Chemistry

Self Cite

View full text Add to dashboard Cite

show abstract

“…Two (E 301 XXH 304 and E 356 XXH 359 in Fig. 2) of the three EXXH motifs conserved in M. grisea, N. crassa and all higher plant sequences have been suggested to be involved in forming the di-iron center of the enzyme (Siedow et al 1995).…”

Section: Discussionmentioning

confidence: 99%

Characterization of two genes encoding the mitochondrial alternative oxidase in Chlamydomonas reinhardtii

Dinant¹,

Baurain²,

Coosemans³

et al. 2001

Current Genetics

View full text Add to dashboard Cite

Two cDNA clones (AOX1 and AOX2) and the corresponding genes encoding the alternative oxidases (AOXs) from Chlamydomonas reinhardtii were isolated and sequenced. The cDNAs, AOX1 and AOX2, contained open reading frames (ORFs) encoding putative proteins of 360 amino acids and 347 amino acids, respectively. For each of the ORFs, a potential mitochondrial-targeting sequence was found in the 5'-end regions. In comparison to AOX enzymes from plants and fungi, the predicted amino acid sequences of the ORFs showed their highest degree of identity with proteins from Aspergillus niger (38.1% and 37.2%) and Ajellomyces capsulatus (37% and 34.9%). Several residues supposed either to be Fe ligands or to be involved in the ubiquinol-binding site were fully conserved in both C. reinhardtii putative AOX proteins. In contrast, a cysteine residue conserved in the sequences of all higher plants and probably involved in the regulation of the enzyme activity was missing both from the AOX1 and AOX2 amino acid sequences and from protein sequences from various other microorganisms. The transcriptional expression of the AOX1 and AOX2 genes in wild-type cells and in mutant cells deficient in mitochondrial complex III activity was also investigated.

show abstract

“…The study of these alternative dehydrogenases and several other aspects of the respiratory chain of A. angustifolia mitochondria are of great importance, especially the study of AOX, as this is a conserved protein along evolution because of its occurrence in fungi, protozoa and plants (Siedow et al, 1995). The Araucariaceae family has an ancient origin in the Triassic Period and the araucarians appear to have maintained a preference for subtropical or mesothermal conditions, illustrated by the present distribution of A. angustifolia in southern Brazil (Kershaw and Wagstaff, 2001).…”

Section: Discussionmentioning

confidence: 99%