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The switching of electron flux from the cyanide-insensitive oxidase to the cytochrome pathway in mung-bean (Phaseolus aureus L.) mitochondria.

ABSTRACT: The activities of the mung-bean (Phaseolus aureus L.) mitochondrial cyanide-insensitive oxidase and cytochrome pathways have been measured simultaneously. The results show that electrons can be diverted both from the alternative pathway to the cytochrome pathway and from the cytochrome to the alternative pathway. The competition of the two pathways for the available electron flux is discussed.

SUBMITTER: Wilson SB

PROVIDER: S-EPMC1148698 | biostudies-other | 1988 Jan

REPOSITORIES: biostudies-other

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Cyanide-insensitive oxidation of ascorbate + NNN'N'-tetramethyl-p-phenylenediamine mixture by mung-bean (Phaseolus aureus) mitochondria. An energy-linked function.

Project description:Freshly prepared washed or purified mung-bean (Phaseolus aureus) mitochondria utilize oxygen with ascorbate/tetramethyl-p-phenylenediamine mixture as electron donor in the presence of KCN. ATP control of the oxygen uptake can be observed with very fresh mitochondria. The electron flow, which is inhibited by antimycin A, salicylhydroxamic acid or octylguanidine, takes place by reversed electron transport through phosphorylation site II and thence to oxygen through the cyanide-insensitive pathway. Oligomycin and low concentrations of uncoupler partially inhibit the oxygen uptake in a manner similar to that observed for other energy-linked functions of plant mitochondria. An antimycin A-insensitive oxygen uptake occurs if high concentrations of uncoupler are used, indicating that the pathway of electron flow has been altered. The process of cyanide-insensitive ascorbate oxidation is self-starting, and, since it occurs in the presence of oligomycin, it is concluded that the reaction can be energized by a single energy-conservation site associated with the cyanide-insensitive oxidase pathway.

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The amino acid sequence of Phaseolus aureua L. (mung-bean) cytochrome c.

Project description:The amino acid sequence of Phaseolus aureus L. (mung-bean) cytochrome c has been determined. The molecule consists of a single polypeptide chain of 111 amino acid residues and is homologous with other mitochondrial cytochromes c. Comparison with the amino acid sequence of wheat-germ cytochrome c (Stevens, Glazer & Smith, 1967) shows 14 differences. On alignment with mammalian cytochromes c, mung-bean cytochrome c has an N-acetylated ;tail' of eight amino acid residues similar to that found in wheat-germ cytochrome c. Of the 22 positions in wheat-germ cytochrome c that contain amino acid residues unique to these positions, 20 were found to contain the same ones in mung-bean cytochrome c. The in-N-trimethyl-lysine residues reported for wheat-germ cytochrome c (Delange, Glazer & Smith, 1969) in positions 72 and 86 were also found in these positions in mung-bean cytochrome c. The sequence was determined from 3mumol, by using chymotryptic and tryptic peptides which were analysed by the ;dansyl'-Edman method (Gray & Hartley, 1963a), with confirmation by amino acid analysis.

| S-EPMC1178845 | biostudies-other

Light-dependent cytochrome P-450 changes in mung beans (Phaseolus aureus).

Project description:Maximum concentrations of microsomal cytochrome P-450 are present in 3-4 day-old mung beans (Phaseolus aureus). On illumination of dark-grown seedlings, cytochrome P-450 and later cytochrome P-450 undergo a rapid decrease in concentration in vivo, with an apparent half-time of about 6 h. Conversely light-grown seedlings, transferred to darkness, show a slow accumulation of cytochrome P-450, doubling time of about 30 h, with a later accumulation of cytochrome P-420. Microsomal cytochromes b559, b560.5 and b562.5 do not significantly alter on light-dark transitions. Possible functions for dark-induced cytochrome P-450 are discussed.

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Structure of the trypanosome cyanide-insensitive alternative oxidase.

Project description:In addition to haem copper oxidases, all higher plants, some algae, yeasts, molds, metazoans, and pathogenic microorganisms such as Trypanosoma brucei contain an additional terminal oxidase, the cyanide-insensitive alternative oxidase (AOX). AOX is a diiron carboxylate protein that catalyzes the four-electron reduction of dioxygen to water by ubiquinol. In T. brucei, a parasite that causes human African sleeping sickness, AOX plays a critical role in the survival of the parasite in its bloodstream form. Because AOX is absent from mammals, this protein represents a unique and promising therapeutic target. Despite its bioenergetic and medical importance, however, structural features of any AOX are yet to be elucidated. Here we report crystal structures of the trypanosomal alternative oxidase in the absence and presence of ascofuranone derivatives. All structures reveal that the oxidase is a homodimer with the nonhaem diiron carboxylate active site buried within a four-helix bundle. Unusually, the active site is ligated solely by four glutamate residues in its oxidized inhibitor-free state; however, inhibitor binding induces the ligation of a histidine residue. A highly conserved Tyr220 is within 4 Å of the active site and is critical for catalytic activity. All structures also reveal that there are two hydrophobic cavities per monomer. Both inhibitors bind to one cavity within 4 Å and 5 Å of the active site and Tyr220, respectively. A second cavity interacts with the inhibitor-binding cavity at the diiron center. We suggest that both cavities bind ubiquinol and along with Tyr220 are required for the catalytic cycle for O2 reduction.

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Mung bean (Phaseolus aureus) nuclease. A mechanistic investigation of the DNA-cleavage reaction using a dinucleoside phosphorothioate.

Project description:Mung-bean (Phaseolus aureus) nuclease has been found to cleave the Sp diastereoisomer of 5'-O-thymidyl 3'-O-(2'-deoxyadenosyl)phosphorothioate, (Sp)-d[Ap(S)T], in 18O-labelled water with inversion of configuration at phosphorus to give (Sp)-thymidine 5'-[16O, 18O]phosphorothioate, the stereochemistry of which was deduced by methylation to (Rp,Sp)-thymidine 5'-S-methyl-O-methyl-[16O,18O]phosphorothioate and 31P-n.m.r. analysis. This result is consistent with a mechanism involving a direct 'in-line' attack of water on DNA for the nuclease-catalysed reaction without the involvement of a covalent nucleotidylated-enzyme intermediate.

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Physiological cyanide concentrations do not stimulate mitochondrial cytochrome c oxidase activity.

Project description: Not available

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Immunomodulation by mung bean

Project description:The immunomodulatory effect of mung bean is mainly attributed to antioxidant properties of flavonoids; however, the precise machinery for biological effect on animal cells remains uncertain. The objective of this study was to understand the physiological change produced by mung bean consumption.

2017-04-06 | PXD005330 | Pride

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Project description:Pseudomonas aeruginosa, an opportunistic pathogen of humans, uses quorum sensing (QS) to regulate the production of extracellular products that can benefit all members of the population. P. aeruginosa can police QS-deficient cheaters by producing hydrogen cyanide, which is also QS regulated; however, the mechanism by which cooperators selectively protect themselves from the toxicity of cyanide remained unresolved. Here, we show that a cyanide-insensitive terminal oxidase encoded by cioAB provides resistance to cyanide, but only in QS-proficient strains. QS-deficient cheaters do not activate cioAB transcription. QS-mediated regulation of cioAB expression depends on production of both cyanide by cooperators (which is QS regulated) and reactive oxygen species (ROS) from cheaters (which is not QS regulated). This type of regulatory system allows cooperating populations to respond, via ROS, to the presence of cheaters, and might allow them to defer the substantial metabolic cost of policing until cheaters are present in the population.

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Lipoxygenase LOX3 Is the Enigmatic Tocopherol Oxidase in Runner Bean (<i>Phaseolus coccineus</i>).

Project description:Purification of extracts from the etiolated seedlings of runner bean (Phaseolus coccineus), coupled with mass spectrometry analysis of proteins revealed that the enzyme responsible for tocopherol oxidation activity is lipoxygenase, an enzyme known for enzymatic lipid peroxidation of unsaturated lipids. Biochemical analysis of the activity, along with the expression profile of three LOX isoforms (LOX1, LOX2, LOX3) in various parts of the etiolated seedlings, revealed that LOX3 was the major isoform expressed in the epicotyls, indicating that this isoform was responsible for the tocopherol oxidation activity; in the primary leaves, besides LOX3, the other two isoforms might have also contributed to the activity. The experiments performed in the model systems showed that unsaturated lipids were not required for the tocopherol oxidase activity, but that lipids were necessary to provide an optimal, hydrophobic environment of the substrate for the reaction. The experiments on lipoxygenase and tocopherol oxidase activities in the leaves of light-grown P. coccineus plants during aging and during storage of the extracts from etiolated seedlings showed that the activity of the first reaction decreased considerably faster than the latter, indicating different mechanisms of both reactions performed by the same enzyme. As LOX3 was shown to occur in the apoplast of the related species P. vulgaris, the question as to the physiological function of LOX3 in the tocopherol oxidation activity in P. coccineus is discussed.

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Plant flavokinase. Affinity-chromatographic procedure for the purification of the enzyme from mung-bean (Phaseolus aureus) seeds and conformational changes on its interaction with orthophosphate.

Project description:Flavokinase was purified, for the first time from a plant source [mung bean (Phaseolus aureus)] by affinity chromatography in the presence of orthophosphate and by using C-8 ATP-agarose (ATP linked through the C-8 position to beaded agarose), Cibacron Blue and riboflavin--Sepharoses. An altered substrates-saturation pattern was observed in the presence of K2HPO4. The conformational changes of the enzyme in the presence of K2HPO4 were monitored by fluorescence spectroscopy. These results highlight the regulatory nature of this enzyme.

| S-EPMC1163074 | biostudies-other

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