Localization and characterization of cytochromes from membrane vesicles of Escherichia coli K-12 grown in anaerobiosis with nitrate |
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Authors: | JoséASánchez Crispín Michel Dubourdieu Marc Chippaux |
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Institution: | Grupo de Biología Experimental, Facultad de Ciencias, Universidad de los Andes, Apartado Postal 281, Mérida, Venezuela |
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Abstract: | Cytochromes b of anaerobically nitrate-grown Escherichia coli cells are analysed. Ascorbate phenazine methosulfate distinguishes low and high potential cytochromes b. Reduction kinetics performed at 559 nm presents a very complex pattern which can be analysed assuming that at least four b-type cytochromes are present. The electron transport chain from formate to oxygen would contain a low potential cytochrome b-556, a cytochrome b-558 associated to the oxidase, and a cytochrome d as the principal oxidase. Cytochrome o is also present, but seems to be functional only at low oxygen concentrations. A cytochrome b-556 associated to nitrate reductase is shown to belong to a branch of the formate-oxidase chain.2-N-Heptyl-4-hydroxyquinoline-N-oxide affects the reduction kinetics in a very complex way. One inhibition site is in evidence between cytochrome b-558 and cytochrome d; another between the cytochrome associated to nitrate reductase and the nitrate reductase. A third inhibition site is located in the common part of the formate-nitrate and the formate-oxidase systems.Ascorbate phenazine methosulfate is shown to donate electrons near cytochrome b-558. |
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Keywords: | Nitrate reductase Anaerobiosis Electron transport Membrane vesicle (Escherichia coli) HQNO |
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