Search results for "cytochrome c"
showing 10 items of 129 documents
A spontaneous mitonuclear epistasis converging on Rieske Fe-S protein exacerbates complex III deficiency in mice
2020
We previously observed an unexpected fivefold (35 vs. 200 days) difference in the survival of respiratory chain complex III (CIII) deficient Bcs1lp.S78G mice between two congenic backgrounds. Here, we identify a spontaneous homoplasmic mtDNA variant (m.G14904A, mt-Cybp.D254N), affecting the CIII subunit cytochrome b (MT-CYB), in the background with short survival. We utilize maternal inheritance of mtDNA to confirm this as the causative variant and show that it further decreases the low CIII activity in Bcs1lp.S78G tissues to below survival threshold by 35 days of age. Molecular dynamics simulations predict D254N to restrict the flexibility of MT-CYB ef loop, potentially affecting RISP dyna…
Deoxysarpagine Hydroxylase — A Novel Enzyme Closing a Short Side Pathway of Alkaloid Biosynthesis in Rauvolfia
2002
Microsomal preparations from cell suspension cultures of the Indian plant Rauvolfia serpentina catalyze the hydroxylation of deoxysarpagine under formation of sarpagine. The newly discovered enzyme is dependent on NADPH and oxygen. It can be inhibited by typical cytochrome P450 inhibitors such as cytochrome c, ketoconazole, metyrapone, tetcyclacis and carbon monoxide. The CO-effect is reversible with light (450 nm). The data indicate that deoxysarpagine hydroxylase is a novel cytochrome P450-dependent monooxygenase. A pH optimum of 8.0 and a temperature optimum of 35 degrees C were determined. K(m) values were 25 microM for NADPH and 7.4 microM for deoxysarpagine. Deoxysarpagine hydroxylase…
p53 triggers apoptosis in oncogene-expressing fibroblasts by the induction of Noxa and mitochondrial Bax translocation.
2003
The mechanism of p53-dependent apoptosis is still only partly defined. Using early-passage embryonic fibroblasts (MEF) from wild-type (wt), p53(-/-) and bax(-/-) mice, we observe a p53-dependent translocation of Bax to the mitochondria and a release of mitochondrial Cytochrome c during stress-induced apoptosis. These events proceed independent of zVAD-inhibitable caspase activation, are not prevented by dominant negative FADD (DN-FADD), but are negatively regulated by Mdm-2. Bcl-x(L) expression prevents the release of mitochondrial Cytochrome c and apoptosis, but not Bax translocation. At a single-cell level, enforced expression of p53 is sufficient to induce Bax translocation and Cytochrom…
Apoptosis induced in hepatoblastoma HepG2 cells by the proteasome inhibitor MG132 is associated with hydrogen peroxide production, expression of Bcl-…
2002
This report is focused on the apoptotic effect induced by MG132, an inhibitor of 26S proteasome, in human hepatoma HepG2 cells. The results were compared with those obtained with non-transformed human Chang liver cells. MG132 reduced the viability of HepG2 cells in a time- and dose-dependent manner. The effect was in tight connection with the induction of apoptosis, as indicated by fluorescence microscopy and cytometric analysis, and was accompanied by a remarkable increase in the production of H2O2 and a reduction in mitochondrial transmembrane potential (Deltapsim). In addition cell death was prevented by antioxidants such as GSH, N-acetylcysteine or catalase. Western blot analysis showed…
Larval morphology, genetic divergence, and contrasting levels of host manipulation between forms of Pomphorhynchus laevis (Acanthocephala)
2004
Studies on parasite species with a wide geographic and ecological range may be confounded by still equivocal taxonomic identification. Here, we investigated genetic polymorphism and behavioural changes induced in a common intermediate host, in two different forms of Pomphorhynchus laevis based on the morphology of the larval infective stage (cystacanth). A 'smooth type' (S) and a 'wrinkled type' (W) of cystacanth were distinguished based on their surface and shape. We analysed sequence divergence at both nuclear (ribosomal gene 18S rDNA, and ribosomal internal transcribed spacers, ITS1/ITS2) and mitochondrial (cytochrome c oxidase subunit 1) genes of P. laevis cystacanths and adults at vari…
Local dynamic properties of the heme pocket in native and solvent-induced molten-globule-like states of cytochrome c
2002
We report the Soret absorption band, down to cryogenic temperature, of native and molten-globule-like state of horse heart cytochrome c. The band profile is analyzed in terms of vibronic coupling of the heme normal modes to the electronic transition in the framework of the Franck-Condon approximation. From the temperature dependence of the Gaussian broadening and of the peak position, we obtain information on the 'bath' of low frequency harmonic motions of the heme group within the heme pocket. The reported data indicate that, compared to the native state, the less rigid tertiary structure of the molten globule is reflected in a higher flexibility of the heme pocket and in greater conformat…
Effects of the herbicides Benzoylpropethyl and flampropisopropyl on rat liver mitochondria : an alteration in membrane fluidity ?
1984
Abstract The action of the herbicides benzoylpropethyl and flampropisopropyl, and the corresponding unesterified acids was studied in rat liver mitochondria. The herbicides were found to (a) inhibit the mitochondrial electron transfer in complex III or at the level of ubiquinone (I50 of 4 nmol mg protein−1 for flampropisopropyl and 18 for benzoylpropethyl with succinate as a substrate); (b) have an additional (however less sensitive) site of inhibition near succinate dehydrogenase; and (c) interfere with energy transfer. Sensitivity was increased 2- (benzoylpropethyl) and 3.5-fold (flampropisopropyl) as the rats age increased from 12–13 weeks to 23–26 weeks. The free acids were far less eff…
Iron Porphyrins as Models of Cytochromec Oxidase
2001
A series of iron porphyrins has been synthesized as models of cytochrome c oxidase; their activity as 4 e− catalysts in the reduction of dioxygen has been studied at pH 7. These compounds have been obtained by grafting very different residues onto the same iron complex, namely tripodal tetraamines, pickets, and straps, in order to change the environment of the metal center. In the case of porphyrins bearing a tripodal cap, the secondary amines have been alkylated with different substituents so as to modify the electronic environment of the distal pocket. Surprisingly, when the iron porphyrin is functionalized with four identical acrylamido pickets, the resulting complex exhibits biomimetic …
Identification of a novel compound heterozygote SCO2 mutation in cytochrome c oxidase deficient fatal infantile cardioencephalomyopathy
2006
UNLABELLED Fatal infantile cardioencephalomyopathy (OMIM No. 604377) is a disorder of the mitochondrial respiratory chain and is characterised by neonatal progressive muscular hypotonia and cardiomyopathy because of severe Cytochrome c oxidase deficiency. Here we report a novel mutation in the Cytochrome c oxidase assembly gene SCO2 in an infant with fatal infantile cardioencephalomyopathy despite normal initial metabolic screening. CONCLUSION In newborns with unexplained muscular hypotonia and cardiomyopathy genetic testing of mitochondrial respiratory chain disorders might be helpful to establish a final diagnosis and guide treatment decisions.
Electrocatalytic reduction of dioxygen to water by tren-capped porphyrins, functional models of cytochrome c oxidase
1999
International audience; Two different tren-capped porphyrins—in which the two metals, iron and copper, are more or less off-centered—are shown to be efficient catalysts for the reduction of O2 to H2O; surprisingly, their iron-only complexes are shown to be even more effective 4e- catalysts when adsorbed on a graphiteelectrode.