The nature of CuA in cytochrome c oxidase

The isolation and purification of yeast cytochrome c oxidase is described. Characterization of the purified protein indicates that it is spectroscopically identical with cytochrome c oxidase isolated from beef heart. Preparations of isotopically substituted yeast cytochrome c oxidase are obtained incorporating [1,3-15N2]histidine or [beta,beta- 2H2]cysteine. Electron paramagnetic resonance and electron nuclear double resonance spectra of the isotopically substituted proteins identify unambiguously at least 1 cysteine and 1 histidine as ligands to CuA and suggest that substantial spin density is delocalized onto a cysteine sulfur in the oxidized protein to render the site Cu(I)-S

Studies on the Cytochrome C Oxidase Activities and Analysis of the Glycolysis and High Energy Phosphorus Compounds in the Normal Bacteria and those Fast to the Antibacterial Com­pounds.

The following results were obtained through the experiments on the cytochrome c oxidase activities and the analysis of the glycolysis and high energy phosphorus compounds in the normal bacteria and those fast to penicillin, sulfathiazol, 2.4-dimethylthiazdl, and macramin. 1. In the normal bacteria, the cytochrome c oxidase activities, glycolysis and high energy phosphorylated cycles increase accordto the order of S.57 s-type&#60;S.57 r-type&#60;staphylococcus aureus F. D. A. strain &#60;staphylococcus aureus Terazima strain. 2. In the bacteria fast to penicillin originated these normal bacterial strain, the cytochrome c oxidase activities, glycolysis and high energy phosphorylated cycles increase, especially glycolysis. 3. In the bacteria fast to sulfathiazol, there are shown the same results as in the case of penicillin. 4. In the bacteria fast to 2.4-dimethylthiazol, the cytochrome c oxidase activities decrease, glycolysis increases markedly and high energy phosphorylated cycle decreases. 5. In the bacteria fast to macramin, these activities and cycles show no specific changes.</p

Histidine is the axial ligand to cytochrome alpha 3 in cytochrome c oxidase

The nitric oxide-bound complexes of reduced yeast cytochrome c oxidase incorporated with [1,3-15N2]histidine have been investigated by EPR spectroscopy. The results of this study have allowed the unambiguous identification of histidine as the endogenous axial ligand to cytochrome alpha 3

Alignment of the amino terminal amino acid sequence of human cytochrome c oxidase subunits I and II with the sequence of their putative mRNAs

Thirteen of the first fifteen amino acids from the NH2-terminus of the primary sequence of human cytochrome c oxidase subunit I and eleven of the first twelve amino acids of subunit II have been identified by microsequencing procedures. These sequences have been compared with the recently determined 5'-end proximal sequences of the HeLa cell mitochondrial mRNAS and unambiguously aligned with two of them. This alignment has allowed the identification of the putative mRNA for subunit I, and has shown that the initiator codon for this subunit is only three nucleotides away from the 5'-end of its mRNA; furthermore, the results have substantiated the idea that the translation of human cytochrome c oxidase subunit II starts directly at the 5'-end of its putative mRNA, as had been previously inferred on the basis of the sequence homology of human mitochondrial DNA with the primary sequence of the bovine subunit

Senile Cataract and the Absorption Activity of Cytochrome C Oxidase

The aim of the study was to determine the activity of cytochrome c oxidase in mitochondrial fractions of cataractogenic epithelial cells of lenses of 60 patients (34 females and 26 males). According to clinical criteria patients were divided into three groups: group 1 – patients with senile cataract, group 2 – active smokers with senile cataract, and group 3 – diabetic patients with cataract as diabetic complication. In the extracted lenses we determined the absorption activity of mitochondrial enzyme cytochrome c oxidase. Biochemical researches using the method of Yonetani and Ray13 were applied. We also applied the statistical Student t-test (p < 0.05) and the variance analysis (R. Fisher) with three parameters and Snedecor F distribution (s = p < 0.001). The activity of cytochrome c oxidase in mitochondrial fraction of lens epithelial cells is twice as low in patients who are active smokers than in the non-smoking patients with senile cataract. We measured a significantly different activity of cytochrome c oxidase between active smokers and the non-smoking patients with senile diabetic cataract (tp < 0.05, sp < 0.001). Cigarette smoke decreases the activity of cytochrome c oxidase in mitochondrial fraction of lens epithelial cells. This enzyme is a terminal oxidase in the synthesis of ATPs. We suggest that smoking decreases the synthesis of energy in the lens of cigarette smokers. This emphasizes the significance of giving up smoking in order to preserve the structure and function of the lens

COA6 facilitates cytochrome c oxidase biogenesis as thiol-reductase for copper metallochaperones in mitochondria.

The mitochondrial cytochrome c oxidase, the terminal enzyme of the respiratory chain, contains heme and copper centers for electron transfer. The conserved COX2 subunit contains the CuA site, a binuclear copper center. The copper chaperones SCO1, SCO2, and COA6 are required for CuA center formation. Loss of function of these chaperones and the concomitant cytochrome c oxidase deficiency cause severe human disorders. Here we analyzed the molecular function of COA6 and the consequences of COA6 deficiency for mitochondria. Our analyses show that loss of COA6 causes combined complex I and complex IV deficiency and impacts membrane potential driven protein transport across the inner membrane. We demonstrate that COA6 acts as a thiol-reductase to reduce disulphide bridges of critical cysteine residues in SCO1 and SCO2. Cysteines within the CX3CXNH domain of SCO2 mediate its interaction with COA6 but are dispensable for SCO2-SCO1 interaction. Our analyses define COA6 as thiol-reductase, which is essential for CuA biogenesis

Biallelic variants in COX4I1 associated with a novel phenotype resembling Leigh syndrome with developmental regression, intellectual disability, and seizures

Autosomal recessive COX4I1 deficiency has been previously reported in a single individual with a homozygous pathogenic variant in COX4I1, who presented with short stature, poor weight gain, dysmorphic features, and features of Fanconi anemia. COX4I1 encodes subunit 4, isoform 1 of cytochrome c oxidase. Cytochrome c oxidase is a respiratory chain enzyme that plays an important role in mitochondrial electron transport and reduces molecular oxygen to water leading to the formation of ATP. Defective production of cytochrome c oxidase leads to a variable phenotypic spectrum ranging from isolated myopathy to Leigh syndrome. Here, we describe two siblings, born to consanguineous parents, who presented with encephalopathy, developmental regression, hypotonia, pathognomonic brain imaging findings resembling Leigh‐syndrome, and a novel homozygous variant on COX4I1, expanding the known clinical phenotype associated with pathogenic variants in COX4I1

Carbon Monoxide-Driven Reduction of Ferric Heme and Heme Proteins

Oxidized cytochrome c oxidase in a carbon monoxide atmosphere slowly becomes reduced as shown by changes in its visible spectra and its reactivity toward oxygen. The \u27autoreduction\u27 of cytochrome c oxidase by this procedure has been used to prepare mixed valence hybrids. We have found that this process is a general phenomenon for oxygen-binding heme proteins, and even for isolated hemin in basic aqueous solution. This reductive reaction may have physiological significance. It also explains why oxygen-binding heme proteins become oxidized much more slowly and appear to be more stable when they are kept under a CO atmosphere. Oxidized α and β chains of human hemoglobin become reduced under CO much more slowly than does cytochrome c oxidase, where the CO-binding heme is coupled with another electron accepting metal center. By observing the reaction in both the forward and reverse direction, we have concluded that the heme is reduced by an equivalent of the water-gas shift reaction (CO + H2O → CO2 + 2e- + 2H+). The reaction does not require molecular oxygen. However, when the CO-driven reduction of cytochrome c oxidase occurs in the presence of oxygen, there is a competition between CO and oxygen for the reduced heme and copper of cytochrome a3. Under certain conditions when both CO and oxygen are present, a peroxide adduct derived from oxygen reduction can be observed. This \u27607 nm complex\u27, described in 1981 by Nicholls and Chanady, forms and decays with kinetics in accord with the rate constants for CO dissociation, oxygen association and reduction, and dissociation of the peroxide adduct. In the absence of oxygen, if a mixture of cytochrome c and cytochrome c oxidase is incubated under a CO atmosphere, autoreduction of the cytochrome c as well as of the cytochrome c oxidase occurs. By our proposed mechanism this involves a redistribution of electrons from cytochrome a3 to cytochrome a and cytochrome c