Studies on cyanide-resistant respiration

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1) Alternative oxidase constitutes a cyanide-resistant reapiratory pathway in the mitochondria of the yeast Hansenula anomala. The expression of nuclear-encoded gene of this enzyme is highly regulated depending upon the various conditions. The genomic DNA was cloned from H. anomala and analyzed. In the upstream region, UAS2-like element was detected. The gel mobility shift assay also suggests the possible involvement of this element in the carbon source-dependent regulation of the gene expression.2) The gene expression of alternative oxidase is induced by Qi site inhibitors and SH compounds in H. anomala. When the cells were pre-treated with pyrithione, zinc ionophore, and chelator, such as EDTA, the expression of alternative oxidase mRNA upon the addition of antimycin A was completely suppressed. The recovery ofmRNA level was observed by the addition of zinc ions. Accordingly, zinc ion is suggested to be involved in the expression machinery of alternative oxidase gene.3) Trypanosome alternative oxidase is the sole terminal oxidase of the respiratory chain of long slender bloodstream forms of African trypanosomes. A cDNA encoding the oxidase from Trypanosoma brucei brucei was cloned and expressed in Escherichia coli. The functional expression of the oxidase in E. coli indicates that the antibiotic, ascofuranone, specifically inhibits the ubiquinol oxidation site of trypanosome alternative oxidase.