Abstract
RESPIRATORY-CHAIN phosphorylation in a particulate fraction of Azotobacter vinelandii is inactivated by incubation of the suspension in salt concentrations less than 0.01 M potassium chloride or sodium chloride, or 0.0008 M magnesium chloride, manganese chloride or calcium chloride. This inactivation is partially reversed by adding salts back to the inactivated suspension1. It has now been found that the inactivated suspension can be fractionated by centrifugation at 50,000 g for 30 min. The sediment contained 85–90 per cent of the reduced diphosphopyridine nucleotide oxidase activity, but restoration of oxidative phosphorylation was not possible unless the suspension was pre-incubated with the supernatant from this high-speed centrifugation, as well as with magnesium chloride (Table 1). Although after pre-incubation this supernatant alone also catalysed oxidative phosphorylation, the oxidase activity was much too low to account for the increased P:O ratio obtained with particles pre-incubated with magnesium chloride and supernatant. It appears, therefore, that the supernatant contains a factor which is necessary for the restoration of the activity of inactivated particles. This factor is destroyed by heating for 5 min. at 100°.
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HOVENKAMP, H. Fractionation of the System Bringing About Oxidative Phosphorylation in Azotobacter vinelandii . Nature 184, 471 (1959). https://doi.org/10.1038/184471a0
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DOI: https://doi.org/10.1038/184471a0
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