Site of action of nonheme iron in the malate (flavine adenine dinucleotide) pathway of Mycobacterium phlei

Irradiation with ultraviolet light (360 nm) of cell-free extracts, electron-transport particles, and soluble components from Mycobacterium phlei resulted in the loss of malate oxidation by the flavine adenine dinucleotide pathway both in cell-free extracts and reconstituted systems. Addition of vitamin K1 restored the loss to the extent of 14% and 11% in cell-free extracts and reconstituted systems respectively. Electron-transport particles from M. phlei upon reduction with malate exhibited electron-paramagnetic resonance signals at g = 2.002 and 1.94, characteristic of napthosemiquinone and nonheme iron protein, respectively. Upon irradiating the particles with ultraviolet light (360 nm) these signals were not observed. Particulate flavine-adenine-dinucleotide-dependent malate dehydrogenase (EC 1.1.1.37) of M. phlei assayed by the 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyl tetrazolium bromide and phenazine methosulfate–2,6-dichlorophenolindophenol systems, which trap electrons at cytochrome c and at the flavine level respectively, was inhibited by o-phenanthroline. These observations suggest that nonheme iron protein is sensitive to ultraviolet light (360 nm) and participates before or in combination with flavine in the malate (flavine adenine dinucleotide) pathway of M. phlei.

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RESPIRATION AND PROTEIN SYNTHESIS IN ESCHERICHIA COLI MEMBRANE-ENVELOPE FRAGMENTS

The Journal of Cell Biology ◽

10.1083/jcb.51.3.664 ◽

1971 ◽

Vol 51 (3) ◽

pp. 664-673 ◽

Cited By ~ 6

Author(s):

Richard W. Hendler

Keyword(s):

Escherichia Coli ◽

Nadh Oxidase ◽

Protein Complexes ◽

Nonheme Iron ◽

Paramagnetic Resonance ◽

Iron Protein ◽

Membrane Envelope ◽

Epr Signal ◽

Almost All ◽

Electron Paramagnetic

The sensitivity of nicotinamide adenine dinucleotide (NADH) oxidase and succinoxidase to metal chelators, the generation of an electron paramagnetic resonance (EPR) signal upon addition of these substrates, and the rate of formation of the EPR signal relative to the rate of the cytochrome reduction suggest the participation of nonheme iron proteins in the respiratory process of Escherichia coli. The most inhibitory metal chelator, thenoyltrifluoro acetone, inhibited the reduction of nonheme iron and cytochromes but did not prevent the reoxidation of the reduced forms. The EPR signal, dehydrogenase, and oxidase activities evoked by NADH are considerably greater than the corresponding activities evoked by succinate. Because both substrates can reduce almost all of the cytochromes, a model in which fewer succinate dehydrogenase-nonheme iron protein complexes are linked to a common cytochrome chain than NADH dehydrogenase-nonheme iron protein complexes is considered likely.

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Simulation of the electron-paramagnetic-resonance spectrum of the iron-protein of nitrogenase. A prediction of the existence of a second paramagnetic centre

Biochemical Journal ◽

10.1042/bj1750955 ◽

1978 ◽

Vol 175 (3) ◽

pp. 955-957 ◽

Cited By ~ 18

Author(s):

D J Lowe

Keyword(s):

Electron Paramagnetic Resonance ◽

Electron Paramagnetic Resonance Spectrum ◽

Complex Formation ◽

Resonance Spectrum ◽

The Other ◽

Paramagnetic Centre ◽

Paramagnetic Resonance ◽

Iron Protein ◽

Integrated Intensities ◽

Electron Paramagnetic

The e.p.r. spectra of the Fe-proteins of nitrogenase from all sources studied have unusual features in that they have very anisotropic linewidths and low integrated intensities. These characteristics can be explained by assuming that one of the two electrons accepted by these proteins is located at a rapidly relaxing paramagnetic centre that is unobservable by e.p.r., but causes anisotropic broadening of the e.p.r. signal of the other electron. Complex-formation between Fe-proteins and MgATP is described in terms of a 50-60 degrees rotation of the e.p.r.-observable centre.

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