Exploring the molecular nature of alternative oxidase regulation and catalysis

Affourtit, Charles; Albury, Mary S.; Crichton, Paul G.; Moore, Anthony L.

doi:10.1016/s0014-5793(01)03261-6

Cited by 119 publications

(71 citation statements)

References 53 publications

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“…This second model was also supported by the newly available sequence data of several fungal AOXs (Joseph-Horne et al 2000). In the new model, the transmembrane domains are no longer structurally tenable, and the hydrophobic part of the protein is believed to associate with the inner membrane, thereby making AOX an interfacial membrane protein (Andersson and Nordlund 1999;Affourtit et al 2002;Fig. 4).…”

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confidence: 88%

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Alternative oxidase: an inter-kingdom perspective on the function and regulation of this broadly distributed 'cyanide-resistant' terminal oxidase

McDonald¹

2008

Functional Plant Biol.

114

106

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Abstract. Alternative oxidase (AOX) is a terminal quinol oxidase located in the respiratory electron transport chain that catalyses the oxidation of quinol and the reduction of oxygen to water. However, unlike the cytochrome c oxidase respiratory pathway, the AOX pathway moves fewer protons across the inner mitochondrial membrane to generate a proton motive force that can be used to synthesise ATP. The energy passed to AOX is dissipated as heat. This appears to be very wasteful from an energetic perspective and it is likely that AOX fulfils some physiological function(s) that makes up for its apparent energetic shortcomings. An examination of the known taxonomic distribution of AOX and the specific organisms in which AOX has been studied has been used to explore themes pertaining to AOX function and regulation. A comparative approach was used to examine AOX function as it relates to the biochemical function of the enzyme as a quinol oxidase and associated topics, such as enzyme structure, catalysis and transcriptional expression and post-translational regulation. Hypotheses that have been put forward about the physiological function(s) of AOX were explored in light of some recent discoveries made with regard to species that contain AOX. Fruitful areas of research for the AOX community in the future have been highlighted.

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confidence: 88%

“…proposed that the presence of a hydroxyl moiety in this location is important as Y radicals can be involved in reduction and oxidation mechanisms involving oxygen (Berthold et al 2000;Affourtit et al 2002).…”

Section: Catalysis: Residues Important For Aox Quinol Oxidase Activitymentioning

confidence: 99%

Alternative oxidase: an inter-kingdom perspective on the function and regulation of this broadly distributed 'cyanide-resistant' terminal oxidase

McDonald¹

2008

Functional Plant Biol.

114

106

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“…The protein is not detectable under standard growth conditions. Its expression is strongly induced by mutations or chemicals that inhibit the ETC, and significant regulation occurs at the level of transcription (Lambowitz et al 1989;Li et al 1996;Lorin et al 2001;Affourtit et al 2002;Tanton et al 2003;Descheneau et al 2005;Chae et al 2007a,b). In higher plants, AOX expression depends on developmental signals, stress conditions, and inhibition of the respiratory chain (reviewed in Clifton et al 2006).…”

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confidence: 99%

Mutations in Two Zinc-Cluster Proteins Activate Alternative Respiratory and Gluconeogenic Pathways and Restore Senescence in Long-Lived Respiratory Mutants ofPodospora anserina

et al. 2009

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In Podospora anserina, inactivation of the respiratory chain results in a spectacular life-span extension. This inactivation is accompanied by the induction of the alternative oxidase. Although the functional value of this response is evident, the mechanism behind it is far from understood. By screening suppressors able to reduce the life-span extension of cytochrome-deficient mutants, we identified mutations in two zinc-cluster proteins, RSE2 and RSE3, which are conserved in other ascomycetes. These mutations led to the overexpression of the genes encoding the alternative oxidase and the gluconeogenic enzymes, fructose-1, 6 biphosphatase, and pyruvate carboxykinase. Both RSE2 and RSE3 are required for the expression of these genes. We also show that, even in the absence of a respiratory deficiency, the wild-type RSE2 and RSE3 transcription factors are involved in life-span control and their inactivation retards aging. These data are discussed with respect to aging, the regulation of the alternative oxidase, and carbon metabolism.

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“…Mitochondria from many higher plants possess, in addition to the conventional cytochrome c oxidase, a second terminal oxidase that oxidizes ubiquinol (1)(2)(3). In thermogenic plants this alternative oxidase (AOX) 6 plays a key role in the release of heat for pollination purposes or for maintaining a warm environment within the flower at low ambient temperatures.…”

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confidence: 99%

Three Redox States of Trypanosoma brucei Alternative Oxidase Identified by Infrared Spectroscopy and Electrochemistry

Maréchal

Kido

Kita

et al. 2009

Journal of Biological Chemistry

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Electrochemistry coupled with Fourier transform infrared (IR) spectroscopy was used to investigate the redox properties of recombinant alternative ubiquinol oxidase from Trypanosoma brucei, the organism responsible for African sleeping sickness.Stepwise reduction of the fully oxidized resting state of recombinant alternative ubiquinol oxidase revealed two distinct IR redox difference spectra. The first of these, signal 1, titrates in the reductive direction as an n ‫؍‬ 2 Nernstian component with an apparent midpoint potential of 80 mV at pH 7.0. However, reoxidation of signal 1 in the same potential range under anaerobic conditions did not occur and only began with potentials in excess of 500 mV. Reoxidation by introduction of oxygen was also unsuccessful. Signal 1 contained clear features that can be assigned to protonation of at least one carboxylate group, further perturbations of carboxylic and histidine residues, bound ubiquinone, and a negative band at 1554 cm ؊1 that might arise from a radical in the fully oxidized protein. A second distinct IR redox difference spectrum, signal 2, appeared more slowly once signal 1 had been reduced. This component could be reoxidized with potentials above 100 mV. In addition, when both signals 1 and 2 were reduced, introduction of oxygen caused rapid oxidation of both components. These data are interpreted in terms of the possible active site structure and mechanism of oxygen reduction to water.Mitochondria from many higher plants possess, in addition to the conventional cytochrome c oxidase, a second terminal oxidase that oxidizes ubiquinol (1-3). In thermogenic plants this alternative oxidase (AOX) 6 plays a key role in the release of heat for pollination purposes or for maintaining a warm environment within the flower at low ambient temperatures. In nonthermogenic plants its function is still under debate; proposed roles include maintaining tricarboxylic acid cycle turnover under high cytosolic phosphorylation potentials, defense against oxidative stress, and growth rate and energy charge homeostasis (4). AOX is also found in species of fungi, green algae, bacteria, and protozoa (5) and, more recently, in mollusks, nematodes, and chordates (6). Of particular importance, however, is its presence in pathogenic protozoa such as the blood parasite Trypanosoma brucei (7) and the intestinal parasite Cryptosporidium parvum (8, 9). T. brucei is a parasite that causes African sleeping sickness in humans and Nagana in livestock and is transmitted by the tsetse fly (7). The bloodstream forms of T. brucei appear to depend solely on its alternative oxidase (TAO) for respiration. Because the protein is absent from the mammalian host, TAO is an attractive and important chemotherapeutic target for African trypanosomiasis (7-10). In this respect it is interesting to note that ascofuranone, isolated from the pathogenic fungus Ascochyta visiae, specifically and potently inhibits the quinol oxidase activity of TAO (11) and rapidly kills the parasites. In addition, the chemotherapeutic eff...

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Exploring the molecular nature of alternative oxidase regulation and catalysis

Cited by 119 publications

References 53 publications

Alternative oxidase: an inter-kingdom perspective on the function and regulation of this broadly distributed 'cyanide-resistant' terminal oxidase

Alternative oxidase: an inter-kingdom perspective on the function and regulation of this broadly distributed 'cyanide-resistant' terminal oxidase

Mutations in Two Zinc-Cluster Proteins Activate Alternative Respiratory and Gluconeogenic Pathways and Restore Senescence in Long-Lived Respiratory Mutants ofPodospora anserina

Three Redox States of Trypanosoma brucei Alternative Oxidase Identified by Infrared Spectroscopy and Electrochemistry

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