Abstract.
We determined the fraction of ‘slow’ and ‘fast’ conformations of bovine cytochrome c oxidase, following the kinetics of cyanide binding to the oxidized enzyme. We investigated whether treatment of heart mitochondrial particles with different commercially available types of cholate (standard and ultra-pure) can affect the fraction of cytochrome c oxidase in the two states. Compared to standard cholate, the use of ultra-pure cholate for solubilization of heart mitochondrial particles significantly increased the fraction of the fast enzyme. Complete homogeneity (∼100% fast) was observed when cytochrome c oxidase was solubilized with ultra-pure cholate from heart mitochondrial particles pre-equilibrated with AMP; equilibration with ADP yielded a much smaller fraction of fast enzyme (∼35%). These observations are discussed on the basis of the structural relationships between the known cholate-binding site and the binuclear cytochrome a3-CuB site: variation in the occupancy of this binding site with cholate or nucleotides may modify reactivity of the oxidized binuclear centre towards cyanide.
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Received 23 June 2000; received after revision 21 July 2000; accepted 31 July 2000
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Shoji, K., Giuffrè, A., D’Itri, E. et al. The ratio between the fast and slow forms of bovine cytochrome c oxidase is changed by cholate or nucleotides bound to the cholate-binding site close to the cytochrome a3/CuB binuclear centre . CMLS, Cell. Mol. Life Sci. 57, 1482–1487 (2000). https://doi.org/10.1007/PL00000631
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DOI: https://doi.org/10.1007/PL00000631