Various protolytic residues in subunit I of aa3-600 quinol oxidase of the aerobic Gram-positive Bacillus subtilis were mutagenized to nonpolar residues. Two of the mutations, Y284F and K304L, impaired the bioenergetic function of the microorganism. The Y284F mutation suppressed the electron-transfer activity of quinol oxidase and altered its interaction with CO and H2O2, thus showing destructio...

Cytochrome b is the central redox catalytic subunit of the quinol: cytochrome c or plastocyanin oxidoreductases. It is involved in the binding of the quinone substrate and it is responsible for the transmembrane electron transfer by which redox energy is converted into a protonmotive force. Cytochrome b also contains the sites to which various inhibitors and quinone antagonists bind and, conseq...

Alternative oxidase (AOX) is a respiratory oxidase found in certain eukaryotes and bacteria; however, its role in bacterial physiology is unclear. Exploiting the genetic tractability of the bacterium Vibrio fischeri, we explore the regulation of aox expression and AOX function. Using quantitative PCR and reporter assays, we demonstrate that aox expression is induced in the presence of nitric ox...

[n the preceding paper it was shown that the average sum of the glucuronic acid and ethereal sulphate conjugations ofrabbits receiving benzene orally was about 20 %, and it was assumed that the conjugates excreted were those of phenolic substances. Of these phenols about one half was shown quantitatively to be phenol whereas the other half was probably a mixture of other phenols such as catecho...

Cytochrome bd is a prokaryotic terminal oxidase that catalyses the electrogenic reduction of oxygen to water using ubiquinol as electron donor. Cytochrome bd is a tri-haem integral membrane enzyme carrying a low-spin haem b558, and two high-spin haems: b595 and d. Here we show that besides its oxidase activity, cytochrome bd from Escherichia coli is a genuine quinol peroxidase (QPO) that reduce...

The cytochrome bc1 complex is the most widely occurring electron transfer complex capable of energy transduction. Cytochrome bc1 complexes are found in the plasma membranes of phylogenetically diverse photosynthetic and respiring bacteria, and in the inner mitochondrial membrane of all eucaryotic cells. In all of these species the bc1 complex transfers electrons from a low-potential quinol to a...

Time weighted average concentrations of benzene in breathing zone air (measured by diffusive sampling coupled with FID gas chromatography) and concentrations of catechol and quinol in the urine (collected at about 1500 in the second half of a working week and analysed by high performance liquid chromatography) were compared in 152 workers who were exposed to benzene (64 men, 88 women). The conc...

Substantial evidence now exists that intrinsic free-radical scavenging contributes to the receptor-independent neuroprotective effects of estrogens. This activity is inherently associated with the presence of a phenolic A-ring in the steroid. We report a previously unrecognized antioxidant cycle that maintains the "chemical shield" raised by estrogens against the most harmful reactive oxygen sp...

The gram-positive endospore-forming bacterium Bacillus subtilis has, under aerobic conditions, a branched respiratory system comprising one quinol oxidase branch and one cytochrome oxidase branch. The system terminates in one of four alternative terminal oxidases. Cytochrome caa(3) is a cytochrome c oxidase, whereas cytochrome bd and cytochrome aa(3) are quinol oxidases. A fourth terminal oxida...

The cytochrome bc(1) complex is the central enzyme of respiratory and photosynthetic electron-transfer chains. It couples the redox work of quinol oxidation and cytochrome reduction to the generation of a proton gradient needed for ATP synthesis. When the quinone processing Q(i)- and Q(o)-sites of the complex are inhibited by both antimycin and myxothiazol, the flash-induced kinetics of the b-h...