The reactions of the oxidase and reductases ofParacoccus denitrificans with cytochromesc |
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Authors: | Lucile Smith Helen C. Davies |
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Affiliation: | (1) Department of Biochemistry, Dartmouth Medical School, 03577 Hanover, New Hampshire;(2) Department of Microbiology, University of Pennsylvania School of Medicine, 19104-6076 Philadelphia, Pennsylvania |
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Abstract: | Electron transport in theParacoccus denitrificans respiratory chain system is considerably more rapid when it includes the membrane-bound cytochromec552 than with either solubleParacoccus c550 or bovine cytochromec; a pool function for cytochromec is not necessary. Low concentrations ofParacoccus or bovine cytochromec stimulate the oxidase activity. This observation could explain the multiphasic Scatchard plots which are obtained. A negatively charged area on the back side ofParacoccus c which is not present in mitochondrialc could be a control mechanism forParacoccus reactions.Paracoccus oxidase and reductase reactions with bovinec show the same properties as mammalian systems; and this is true ofParacoccus oxidase reactions with its own soluble cytochromec if added polycation masks the negatively charged area. Evidence for different oxidase and reductase reaction sites on cytochromec include: (1) stimulation of the oxidase but not reductase by a polycation; (2) differences in the inhibition of the oxidase and reductases by monoclonal antibodies toParacoccus cytochromec; and (3) reaction of another bacterial cytochromec withParacoccus reductases but not oxidase. Rapid electron transport occurs in cytochromec-less mutants ofParacoccus, suggesting that the reactions result from collision of diffusing complexes. |
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Keywords: | Electron transport respiratory chain cytochromec cytochromec552 cytochromeaa3 cytochromec oxidase cytochromec reductase Paracoccus denitrificans |
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