The 1 equiv reaction between ascorbic acid and cytochrome b(561) is a good model for redox reactions between metalloproteins (electron carriers) and specific organic substrates (hydrogen-atom carriers). Diethyl pyrocarbonate inhibits the reaction of cytochrome b(561) with ascorbate by modifying a histidine residue in the ascorbate-binding site. Ferri/ferrocyanide can mediate reduction of DEPC-t...

Production of superoxide radical during oxidation of dihydroorotate in rat liver mitochondria was not affected by antimycin A, thenoyltrifluoroacetone, or added ubiquinone but was inhibited by orotate, a product inhibitor of dihydroorotate dehydrogenase. It appears likely that superoxide is generated at the primary dehydrogenase. Dihydroorotate dehydrogenase differs from succinate dehydrogenase...

I. An enzyme that catalyzes the reduction of erythrocyte cytochrome b 5 has been isolated from the supernatant fraction of erythrocyte hemolysates by chromatography on DEAE-cellulose, Amberlite CG-5 o, and Bio-Gel P-6o. 2. Erythrocyte cytochrome b 5 reductase has been shown to contain FAD. Incubation of the reductase in the absence of EDTA results in both the appearance of flavin fluorescence a...

Phenobarbital induces liver cytochrome P-450 b,e proteins mainly by increasing the rate of transcription of these genes. The mechanism responsible for the phenobarbital increment in the rate of transcription of cytochrome P-450 b,e genes is unknown. The objective of this study was to assess whether active protein synthesis was needed for phenobarbital to induce the liver cytochrome P-450 b,e ge...

The biosynthesis of mammalian mitochondrial cytochromes was explored in primary hepatocyte cultures. When these were pulsed with [35S]methionine in the presence of cycloheximide, eight discrete mitochondrial polypeptides were detected by fluorography after their resolution under denaturing conditions by polyacrylamide gel electrophoresis. Since the pulse labeling of the polypeptides was sensiti...

The biogenesis and assembly of photosynthetic multisubunit protein complexes is assisted by a series of nucleus-encoded auxiliary protein factors. In this study, we characterize the dac mutant of Arabidopsis (Arabidopsis thaliana), which shows a severe defect in the accumulation of the cytochrome b(6)/f complex, and provide evidence suggesting that the efficiency of cytochrome b(6)/f complex as...

DNA sequences of the complete cytochrome b gene are shown to contain robust phylogenetic signal for the strepsirrhine primates (i.e., lemurs and lorises). The phylogeny derived from these data conforms to other molecular studies of strepsirrhine relationships despite the fact that uncorrected nucleotide distances are high for nearly all intrastrepsirrhine comparisons, with most in the 15%-20% r...

Cytochrome b deficiency in the peripheral granulocytes of two male patients with chronic granulomatous disease was demonstrated by an immunocytochemical assay using a monoclonal antibody, 7D5, against human neutrophil cytochrome b. A mosaic of cytochrome b positive and negative neutrophils, indicating a carrier state in an X-linked trait, was found in the mother of patient 1 but not in the moth...

Cytochrome b558, involved in superoxide generation in phagocytes, was found to be expressed on the cell surface of most normal peripheral B lymphocytes. The cytochrome was not found on the surface of peripheral T lymphocytes, natural killer cells, or peripheral lymphocytes derived from patients with X-linked chronic granulomatous disease. On stimulation, at least half of peripheral B lymphocyte...