Effects of copper concentration in continuous culture on the aa
3-type cytochrome oxidase and respiratory chains of Paracoccus denitrificans |
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Authors: | Julia A Hubbard Martin N Hughes Robert K Poole |
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Institution: | (1) Department of Chemistry, King's College London (Kensington Campus), Campden Hill Road, W8 7AH London, UK;(2) Biosphere Sciences Division, King's College London (Kensington Campus), Campden Hill Road, W8 7AH London, UK;(3) Present address: Department of Biology, University College, Gower Street, WC1E 6BT London, UK |
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Abstract: | The role(s) of copper in a bacterial cytochrome oxidase of the aa
3-type was investigated by growth of Paracoccus denitrificans NCIB 8944, in batch and steady state continuous culture, in a medium from which the bulk of the copper had been extracted. In a medium containing approximately 0.02 M copper, cellular copper content, cytochromes a+a
3 and cytochrome a
3 were reduced to 55%, 58% and 33% respectively of control values and there were also less marked decreases in cytochromes c+c
1 (to 85%) and a CO-binding b-type cytochrome, possibly cytochrome o (to 71%). Copper deficiency elicited in reduced minus oxidized difference spectra a shift to shorter wavelengths and narrowing of the band width of the -band of the oxidase, and loss of a (negative) band near 830 nm attributable to CuA (the copper functionally associated with haem a in the oxidase complex). The oxidase in copper-deficient cells reacted with oxygen to form the oxy Compound A at rates similar to that in control cells but CO recombination to ferrous haem a
3 was slowed 4-fold in the copper deficient case. The results are interpreted as indicating loss of CuA and changes in the proportions of haems a and a
3 with retention of catalytic activity. Titrations of respiration rates with antimycin suggested that copper deficiency did not result in diversion of electron flux through an antimycin A-insensitive, cytochrome o-terminated branch of the respiratory chain. |
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Keywords: | Copper-limitation Escherichia coli Cytochrome oxidases Oxygen reduction Respiratory chains |
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