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Biomedical subjects

O T Jones

Publications and source records attributed to O T Jones.

At least 127 records · Page 7Linked to original sources
PubMed1978

Absence of a newly described cytochrome b from neutrophils of patients with chronic granulomatous disease.

A unique cytochrome b which becomes incorporated into phagocytic vacuoles has been described in human neutrophils. This cytochrome b appears to be situated in the plasma membrane of these cells, and acts as a component of the microbicidal oxidase system. Absence or gross abnormality of this cytochrome b was demonstrated in all four patients with chronic granulomatous disease who were investigated, and reduced concentrations in two mothers known to be carriers of the disease.

Child↗
PubMed1978

Properties of a cytochrome c-enriched light particulate fraction isolated from the photosynthetic bacterium Rhodopseudomonas spheroides.

Differential centrifugation of suspensions of French-press-disrupted Rhodopseudomonas spheroides yielded a light particulate fraction that was different in many properties from the bulk membrane fraction. It was enriched in cytochrome c and had a low cytochrome b content. When prepared from photosynthetically grown cells this fraction had a very low specific bacteriochlorophyll content. The cytochrome c of the light particles differed in absorption maxima at 77K from cytochrome c2 attached to membranes; there was pronounced splitting of the alpha-band, as is found in cytochrome c2 free in solution. Potentiometric titration at A552--A540 showed the presence of two components that fitted an n = 1 titration; one component had a midpoint redox potential of +345mV, like cytochrome c2 in solution, and the second had E0' at pH 7.0 of +110 mV, and they were present in a ratio of approx. 2:3. Difference spectroscopy at 77K showed that the spectra of the two components were very similar. More of a CO-binding component was present in particles from photosynthetically grown cells. Light membranes purified by centrifugation on gradients of 5--60% (w/w) sucrose retained the two c cytochromes; they contained no detectable succinate-cytochrome c reductase or bacteriochlorophyll and very little ubiquinone, but they contained NADH-cytochrome c reductase and some phosphate. Electrophoresis on sodium dodecyl sulphate/polyacrylamide gels showed that the light membranes of aerobically and photosynthetically grown cells were very similar and differed greatly from other membrane fractions of R. spheroides.

Bacterial Chromatophores↗
PubMed1978

Localization of ferrochelatase and of newly synthesized haem in membrane fractions from Rhodopseudomonas spheroides.

Cells of Rhodopseudomonas spheroides, strains R-26 or GVP, were grown photosynthetically, disrupted and two particulate fractions separated by sucrose-density-gradient centrifugation. The upper particulate fraction, enriched in bacteriochlorophyll, was identified as containing the chromatophores; the lower particulate fraction had the characteristics of the cell envelope. The two fractions differed in cytochrome content and cytochrome spectra. Ferrochelatase was found almost exclusively in the chromatophore fraction and was located on the outer face of the chromatophores, i.e. in contact with the cytosol in intact cells. The addition of 59FeCl3 to cells growing in low-iron media resulted in labelling of the protohaem fraction (probably arising from cytochrome b) of the membranes. The specific radioactivity of the haem of the chromatophores rose more rapidly than that of the envelope fraction and then after 2 h declined to approximately the same value, suggesting that haems of the chromatophore may act as precursors of haem of the envelope.

Bacterial Chromatophores↗
PubMed1976

The subcellular loclization and properties of the ferrochelatase of etiolated barley.

The etioplast fraction prepared from dark-grown barley contained the enzyme ferrochelatase. A mitochondrial fraction prepared from the same dark-grown tissue also contained ferrochelatase. After density-gradient centrifugation an etioplast band was collected that was free from detectable mitochondrial marker enzymes and yet retained ferrochelatase activity. A membrane band that was enriched in mitochondria also contained ferrochelatase. The ferrochelatase in these two bands had different pH optima, but appeared very similar in their porphyrin specificity and their inhibition by metalloporphyrins.

Darkness↗
PubMed1975

Detection of two further beta-type cytochromes in Rhodopseudomonas spheroides.

The photosynthetically-incompetent mutant V-2 of Rhodopseudomonas spheroides which is incapable of synthesising bacteriochlorophyll was grown aerobically under conditions of both high and low aeration. Potentiometric titration a at 560 nm minus 570 nm revealed the presence of several different components tentatively identified as b-type cytochromes. Two such components of oxidation-reduction midpoint potentials of +390 mV +/- 10 mV and +255 mV +/- 7mV have not previously been detected in membranes of Rps. spheroides. These components have also been resolved by difference spectra at controlled oxidation-reduction potentials and fourth derivative spectra. Neither component appeared to react with CO. With increasing aeration of the culture medium the relative concentration of these two b-type cytochromes diminished, whilst that of the a-type oxidase increased.

Ascorbic Acid↗
PubMed1975

Protoheme turnover and chlorophyll synthesis in greening barley tissue.

Studies in which (14)C-labeled precursors were fed to etiolated barley leaves (Hordeum vulgare L. var. Proctor) yielded chlorophyll and protoheme having similar specific radioactivities. These findings indicate: (a) there appears to be a rapid turnover of protoheme in the absence of net synthesis; (b) both pigments probably originate from a single 5-aminolevulinic acid pool; (c) the efficient utilization of glutamate-1-(14)C and the relatively poor utilization of glycine-2-(14)C suggest that 5-aminolevulinic acid is probably synthesized by a pathway other than 5-aminolevulinic acid synthetase (succinyl CoA-glycine succinyltransferase) in agreement with previously published work; (d) protoheme turnover appears to be faster under conditions which allow for rapid chlorophyll accumulation; (e) difference spectra indicate that mitochondrial cytochromes make a relatively minor contribution to the total heme in barley leaves. These findings are discussed in the light of current knowledge about tetrapyrrole regulation in photosynthetic organisms.

Journal Article↗