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B T Storey

Publications and source records attributed to B T Storey.

At least 109 records · Page 6Linked to original sources
PubMed1974

The Respiratory Chain of Plant Mitochondria: XVII. Flavoprotein-Cytochrome b(562) Interaction in Antimycin-treated Skunk Cabbage Mitochondria.

During the transition from the aerobic steady state with succinate as substrate to anaerobiosis, in suspensions of skunk cabbage (Symplocarpus foetidus) mitochondria treated with antimycin A, cytochrome b(562) becomes reoxidized to the extent of about 20%, synchronously with the reduction of cytochrome c(549). This reoxidation occurs in both the absence and presence of m-chlorobenzhydroxamic acid, a specific inhibitor for the alternate terminal oxidase of plant mitochondria. A flavoprotein component, amounting to 13% to 15% of the total nonfluorescent mitochondrial flavoprotein, undergoes reduction synchronously with the oxidation of cytochrome b(562) during the aerobic to anaerobic transition with succinate as substrate in the presence of both antimycin A and m-chlorobenzhydroxamic acid. This flavoprotein component remains reduced in the presence of cyanide. The half-time for reduction of the flavoprotein component and cytochrome c(549) and for oxidation of cytochrome b(562) during the aerobic to anaerobic transition with succinate as substrate in the presence of both antimycin A and m-chlorobenzhydroxamic acid is 2 seconds. The half-times for oxidation of cytochrome c(549) and the flavoprotein component are 2.1 and 170 milliseconds, respectively, during the anaerobic to aerobic transition induced by addition of 14 mum O(2) to the mitochondrial suspensions. The half-time for reduction of cytochrome b(562) under these conditions is 150 milliseconds, synchronous with the flavoprotein component. The synchrony of the flavoprotein oxidation and of the cytochrome b(562) reduction at a rate much slower than that of cytochrome c(549) oxidation implies that, in antimycin-treated plant mitochondria, the state of the cytochrome b(562)/antimycin complex is regulated by the redox state of this flavoprotein component, rather than by cytochrome c(549). It is tentatively suggested that these two components are not part of the main sequence of the respiratory chain, but may be part of a multienzyme complex active in the hydroxylation reactions required for ubiquinone biosynthesis in the inner mitochondrial membrane.

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PubMed1972

The Respiratory Chain of Plant Mitochondria: XII. Some Aspects of the Energy-linked Reverse Electron Transport from the Cytochromes c to the Cytochromes b in Mung Bean Mitochondria.

The cytochromes c of mung bean (Phaseolus aureus) mitochondria become reduced when sulfide, a cytochrome oxidase inhibitor free from uncoupling side effects, is added to the aerobic mitochondrial suspension in the absence of added substrate. The cytochromes b remain largely oxidized. Subsequent addition of ATP results in partial oxidation of the cytochromes c and partial reduction of the cytochromes b due to ATP-driven reverse electron transport through the second site of energy conservation, or coupling site, of the respiratory chain. Cytochrome a is also oxidized under these conditions, but there is no concomitant reduction of the flavoprotein components, of ubiquinone, or of endogenous pyridine nucleotide. The reaction is abolished by oligomycin. The reducing equivalents transported from the cytochromes c and a in ATP-driven reverse electron transport are about 2-fold greater than those which appear in the cytochromes b. It is suggested that the equivalents not accounted for are present in a coupling site enzyme at the second site of energy conservation which interacts with the respiratory chain carriers by means of the dithiol-disulfide couple; this couple would not show absorbance changes with redox state over the wavelength range examined. With succinate present, reverse electron transport can be demonstrated at both coupling sites in both the aerobic steady state and in anaerobiosis. ATP-driven reverse electron transport in anaerobiosis maintains cytochrome a 30% oxidized while endogenous pyridine nucleotide is 50% reduced.When mung bean mitochondria, oxidizing succinate in the presence of sulfide through the alternate, cyanide- and sulfide-insensitive terminal oxidase, become anaerobic, cytochrome b(557), which has remained largely oxidized, becomes slowly reduced. The slow reduction is observed in coupled, energized mitochondria and in uncoupled mitochondria; the time course parallels the reduction of cytochrome a(3) under the same conditions. It appears that sulfide-liganded, oxidized cytochrome a(3) may be in close enough proximity to cytochrome b(557) in the membrane to inhibit the reduction of the latter.

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PubMed1972

The Respiratory Chain of Plant Mitochondria: XIV. Ordering of Ubiquinone, Flavoproteins, and Cytochromes in the Respiratory Chain.

The effect of initial oxygen concentration on the rate and extent of oxidation of the respiratory chain carriers of anaerobic mitochondria from mung bean (Phaseolus aureus) seedlings was examined. The substrate was succinate, with malonate added to give malonate to succinate ratios of 6 to 12, thereby minimizing the flow of reducing equivalents from substrate and insuring maximal extent of oxidation of the carriers. The ratio of oxidizing equivalents available from oxygen to reducing equivalents available from reduced ubiquinone, designated the equivalents ratio, varied from 30 to 1. Cytochromes aa(3) and c(547) have unaltered oxidation half-times, designated t((1/2) on), as the equivalents ratio is reduced from 30 to 3, and the extent of oxidation is decreased by about 25%. The time of the oxidation-reduction cycle induced by the oxygen pulse, calculated from the point of half oxidation to that of half reduction and designated t((1/2) off), decreases 200 fold with this reduction in equivalents ratio. The oxidation half-time, t((1/2) on), for ubiquinone is unaltered by decreasing the equivalents ratio from 6 to 1; the value of t((1/2) off) decreases only 30% while the extent of oxidation decreases 50%. The values of t((1/2) on) and t((1/2) off) and the extent of oxidation of cytochrome b(553) and flavoprotein Fp(ha) were all much reduced at low equivalents ratios. The results, plus results from previous studies, indicate that there is the following linear sequence of components in the plant respiratory chain:Dehydrogenase.UQ.Fp(ha).b(553). c(549).a.a(3)Cytochrome b(557) and the low potential flavoproteins do not fit into this linear sequence.

Journal Article↗
PubMed1971

Specific inhibition of the cyanide-insensitive respiratory pathway in plant mitochondria by hydroxamic acids.

Hydroxamic acids, R-CONHOH, are inhibitors specific to the respiratory pathway through the alternate, cyanide-insensitive terminal oxidase of plant mitochondria. The nature of the R group in these compounds affects the concentration at which the hydroxamic acids are effective, but it appears that all hydroxamic acids inhibit if high enough concentrations are used. The benzhydroxamic acids are effective at relatively low concentrations; of these, the most effective are m-chlorobenzhydroxamic acid and m-iodobenzhydroxamic acid. The concentrations required for half-maximal inhibition of the alternate oxidase pathway in mung bean (Phaseolus aureus) mitochondria are 0.03 mm for m-chlorobenzhydroxamic acid and 0.02 mm for m-iodobenzhydroxamic acid. With skunk cabbage (Symplocarpus foetidus) mitochondria, the required concentrations are 0.16 for m-chlorobenzhydroxamic acid and 0.05 for m-iodobenzhydroxamic acid. At concentrations which inhibit completely the alternate oxidase pathway, these two compounds have no discernible effect on either the respiratory pathway through cytochrome oxidase, or on the energy coupling reactions of these mitochondria. These inhibitors make it possible to isolate the two respiratory pathways and study their mode of action separately. These inhibitors also enhance an electron paramagnetic resonance signal near g = 2 in anaerobic, submitochondrial particles from skunk cabbage, which appears to be specific to the alternate oxidase and thus provides a means for its assay.

Cyanides↗
PubMed1971

The Respiratory Chain of Plant Mitochondria: IX. Oxidation-Reduction Potentials of the Cytochromes of Mung Bean Mitochondria.

The oxidation-reduction potentials of the cytochromes of the respiratory chain of mung bean (Phaseolus aureus) mitochondria have been measured under strictly anaerobic conditions with a combined spectrophotometric/potentiometric method. The midpoint potentials at pH 7.2 are as follows: cytochrome a: +190 millivolts; a(3): +380 millivolts; b(553): +75 millivolts; b(557): +42 millivolts; b(562): -77 millivolts; c(547) and c(549): +235 millivolts. (The subscripts refer to the difference absorbance maxima observed for these cytochromes in reduced-minus-oxidized difference spectra recorded at 77 K.) The same values of midpoint potentials at pH 7.2 are obtained with mitochondria depleted of energy by aerobic incubation with ADP and uncoupler in the presence of inorganic phosphate, or with coupled mitochondria energized with ATP in the absence of inorganic phosphate. Coupling site II is placed between b(553)/b(557) and c(549)/c(547) in these mitochondria, and coupling site III is placed between a and a(3).

Journal Article↗
PubMed1971

The respiratory chain of plant mitochondria: x. Oxidation-reduction potentials of the flavoproteins of skunk cabbage mitochondria.

The oxidation-reduction potentials of the flavoproteins of skunk cabbage (Symplocarpus foetidus) mitochondria have been measured under anaerobic conditions by means of a combined spectrophotometric or fluorimetric-potentiometric method. Five components were resolved whose oxidation-reduction reactions corresponded to two-electron changes, as expected for flavoproteins. The midpoint potentials at pH 7.2 are as follows, listed in order of increasingly negative potential: +170 millivolts, +110 millivolts, +20 millivolts, -70 millivolts, and -155 millivolts. The most negative component was highly fluorescent; the other components could only be identified by their characteristic absorbance changes. In addition to these components, which are mitochondrial, variable amounts of a very highly fluorescent flavoprotein with a midpoint potential of -215 millivolts was found. This component appears to be extra-mitochondrial. The same midpoint potential values at pH 7.2 were obtained with mitochondria in the uncoupled state as in mitochondria energized with ATP in the absence of phosphate.

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