Structure and Function of the Plant Alternative Oxidase: Its Putative Role in the Oxygen Defence Mechanism

Wagner, Anneke M.; Moore, Anthony L.

doi:10.1023/a:1027388729586

Cited by 157 publications

(71 citation statements)

References 51 publications

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“…As a terminal ubiquinol oxidase, AOX acts as a mild uncoupler of oxidative phosphorylation and as an antioxidant (50) and prevents an oxidative stress in NCS mutants (3). Thus, in NCS mutants with high constitutive expression of AOX, effective inhibition of ROS generation occurs at the expense of further de-energization of the mitochondrial membrane.…”

Section: Discussionmentioning

confidence: 99%

Mitochondrial Respiratory Deficiencies Signal Up-regulation of Genes for Heat Shock Proteins

Kuzmin

Карпова

Elthon

et al. 2004

Journal of Biological Chemistry

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The consequences of mitochondrial dysfunction are not limited to the development of oxidative stress or initiation of apoptosis but can result in the establishment of stress tolerance. Using maize mitochondrial mutants, we show that permanent mitochondrial deficiencies trigger novel Ca 2؉ -independent signaling pathways, leading to constitutive expression of genes for molecular chaperones, heat shock proteins (HSPs) of different classes. The signaling to activate hsp genes appears to originate from a reduced mitochondrial transmembrane potential. Upon depolarization of mitochondrial membranes in transient assays, gene induction for mitochondrial HSPs occurred more rapidly than that for cytosolic HSPs. We also demonstrate that in the nematode Caenorhabditis elegans transcription of hsp genes can be induced by RNA interference of nuclear respiratory genes. In both organisms, activation of hsp genes in response to mitochondrial impairment is distinct from their responses to heat shock and is not associated with oxidative stress. Thus, mitochondria-to-nucleus signaling to express a hsp gene network is apparently a widespread retrograde mechanism to facilitate cell defense and survival.

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Section: Discussionmentioning

confidence: 99%

Mitochondrial Respiratory Deficiencies Signal Up-regulation of Genes for Heat Shock Proteins

Kuzmin

Карпова

Elthon

et al. 2004

Journal of Biological Chemistry

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“…Preliminary results from our laboratory suggest that both the wild-type and the Y253F mutated AOX exhibit similar sensitivities to the phenolic inhibitors salicylhydroxamic acid and octyl-gallate. 2 This may indicate that Tyr-253 is not involved in quinone binding. It should be emphasized, however, that our steady-state oxygen consumption measurements lack the time resolution to conclusively exclude a role for Tyr-253 in the binding and/or oxidation of ubiquinol.…”

Section: Discussionmentioning

confidence: 99%

“…[1][2][3][4]. This terminal oxidase branches from the cytochrome pathway at the level of the ubiquinone pool and is non-protonmotive.…”

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confidence: 99%

Structure of the Plant Alternative Oxidase

Albury

Affourtit

Crichton

et al. 2002

Journal of Biological Chemistry

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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 (...

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“…In addition to the alternative oxidase (AOX) [1][2][3], some plant mitochondria contain another energy-dissipating system, namely a plant uncoupling mitochondrial protein (PUMP) [4,5]. The cyanide (CN)-and antimycin-resistant AOX, which bypasses the main cytochrome respiratory chain, catalyzes ubiquinol-oxygen oxido-reduction without H + release in the cytosol and thus dissipates redox potential energy [1 3].…”

Section: Introductionmentioning

confidence: 99%

Free fatty acids regulate the uncoupling protein and alternative oxidase activities in plant mitochondria

et al. 1998

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Two energy-dissipating systems, an alternative oxidase and an uncoupling protein, are known to exist in plant mitochondria. In tomato fruit mitochondria linoleic acid, a substrate for the uncoupling protein, inhibited the alternative oxidase-sustained respiration and decreased the ADPIO ratio to the same value regardless of the level of alternative oxidase activity. Experiments with varying concentrations of linoleic acid have shown that inhibition of the alternative oxidase is more sensitive to the linoleic acid concentration than the uncoupling protein activation. It can be proposed that these dissipating systems work sequentially during the life of the plant cell, since a high level of free fatty acid-induced uncoupling protein activity excludes alternative oxidase activity.

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Structure and Function of the Plant Alternative Oxidase: Its Putative Role in the Oxygen Defence Mechanism

Abstract: Current understanding of the structure and function of the plant alternative oxidase is reviewed. In particular, the role of the oxidase in the protection of tissues against oxidative stress is developed.

Cited by 157 publications

References 51 publications

Mitochondrial Respiratory Deficiencies Signal Up-regulation of Genes for Heat Shock Proteins

Mitochondrial Respiratory Deficiencies Signal Up-regulation of Genes for Heat Shock Proteins

Structure of the Plant Alternative Oxidase

Free fatty acids regulate the uncoupling protein and alternative oxidase activities in plant mitochondria

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