A new, nuclear, cytochrome-deficient mutant of Neurospora crassa has been isolated. The mutant is characterized by its slow growth rate, high dependence on the alternate oxidase pathway of respiration, absence of spectrally detectable cytochrome aa3, and low levels of cytochrome c oxidase activity. The amount of cytochrome b appears to be normal in the mutant whereas the amount of cytochrome c ...

chrome oxidase content of tumors, both types of assay methods have not been used concurrently. Experiments described in this communication were designed to provide information about the cytochrome oxidase content of Morris hepatoma 3924A relative to normal, host, and fetal liver by using both the oxygen electrode enzymatic assay (jolarographic assay) and the spectral assay. As will be described...

Mixing ATP with soluble oxidized cytochrome c oxidase induces a spectral perturbation in the Soret region of the enzyme. This spectral perturbation is observed at ATP concentrations similar to those found to modulate the catalytic activity of cytochrome c oxidase [Malatesta, Antonini, Sarti & Brunori (1987) Biochem. J. 248, 161-165]. The process is reversible and corresponds to a simple binding...

Aleem, M. I. H. (Research Institute for Advanced Studies, Baltimore, Md.). Thiosulfate oxidation and electron transport in Thiobacillus novellus. J. Bacteriol. 90:95-101. 1965.-A cell-free soluble enzyme system capable of oxidizing thiosulfate was obtained from Thiobacillus novellus adapted to grow autotrophically. The enzyme systems of autotrophically grown cells brought about the transfer of ...

A simple spectroscopic method for determining the cytochrome c oxidase, cytochrome a, a3, content in tissue and mitochondria samples independent of myoglobin or blood contamination is described. Using tissue homogenates solubilized in Triton X-100, this assay relies on the selective reduction of mitochondrial cytochromes by the action of potassium cyanide. Monitoring the optical absorbance of t...

Rhodobacter sphaeroides 2.4.1(T) respires aerobically via a branched respiratory chain consisting of both cytochrome c oxidases and quinol oxidases. Here, genes from chromosome II encoding two distinct quinol oxidases have been characterized. The qoxBA genes encode a putative heme-copper quinol oxidase, whereas the qxtAB genes encode a quinol oxidase homologous to the cyanide-insensitive oxidas...

Cytochrome bd oxidase operons from more than 50 species of bacteria contain a short gene encoding a small protein that ranges from ∼30 to 50 amino acids and is predicted to localize to the cell membrane. Although cytochrome bd oxidases have been studied for more than 70 years, little is known about the role of this small protein, denoted CydX, in oxidase activity. Here we report that Escherichi...

Nutritional studies have long supported the view that copper may be a part of cytochrome c oxidase (l-3). However, direct evidence did not become available until Eichel et al. (4) found that there was a good correlation between the copper content and the a-absorption by the reduced enzyme in fractions of heart mitochondria prepared with deoxycholate. More recently, Green et al. (5) and Okunuki ...

The recent discovery of small molecules targeting the cytochrome bc1 :aa3 in Mycobacterium tuberculosis triggered interest in the terminal respiratory oxidases for antituberculosis drug development. The mycobacterial cytochrome bc1 :aa3 consists of a menaquinone:cytochrome c reductase (bc1 ) and a cytochrome aa3 -type oxidase. The clinical-stage drug candidate Q203 interferes with the function ...