Cytochromec

Thecaa3-oxidase from Thermus thermophilushas been studied with a combined electrochemical, UV/VIS and Fourier-transform infrared (FT-IR) spectroscopic approach. In this oxidase the electron donor, cytochromec, is covalently bound to subunit II of the cytochrome c oxidase. Oxidative electrochemical redox titrations in the visible spectral range yielded a midpoint potential of )0.01 ± 0.01 V (vs. Ag/AgCl/3MKCl, 0.218 V vs. SHE¢) for the hemec.

9p research12 29-04-2013 49 3   Download

Previous results have shown that theoncoembryonicmarker a-fetoprotein (AFP) is able to induce apoptosis in tumor cells through activation of caspase 3, bypassing Fas-dependent and tumor necrosis factor receptor-dependent signaling. In this study we further investigate the molecular interactions involvedin the AFP-mediatedsignaling of apoptosis. We show that AFP treatment of tumor cells is accompaniedby cytosolic translocation of mitochondrial cytochromec.

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The cytochromec nitrite reductase is isolated from the membranes of the sulfate-reducing bacteriumDesulfovibrio desulfuricansATCC 27774 as a heterooligomeric complex composedby two subunits (61 kDa and19 kDa) containing c-type hemes, encoded by the genes nrfA and nrfH, respectively. The extracted complex has in average a 2NrfA:1NrfH composition. The separation of ccNiR sub-units from one another is accomplished by gel filtration chromatography in the presence of SDS.

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BAP31 is a 28-kDa integral membrane protein of the endoplasmic reticulumwhose cytosolicdomaincontains two caspase recognition sites that are preferentially cleaved by initiator caspases,such as caspase-8. Recently,we reported that the caspase-resistant BAP31 inhibited Fas-mediated apoptotic membrane fragmentation and the release of cytochromec from mitochondria in KB epithelial cells (Nguyen M.,Breckenridge G.,Ducret A &Shore G. (2000) Mol. Cell.Biol.20,6731–6740).

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The influence of temperature on cytochromec oxidase (CCO) catalytic activity was studied in the temperature range 240–308 K. Temperatures below 273 K required the inclusion of the osmolyte ethylene glycol. For steady-state activity between 278 and 308 K the activation energy was 12 kcalÆmol )1 ; the molecular activity or turnover number was 12 s )1 at 280K in the absence of ethylene glycol. CCO activity was studied between 240and 277 K in the presence of ethylene glycol.

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The structure of cytochromec-550 from the nonphotosynthetic bacteria Paraccocus versutushas been solved by X-ray crystallography to 1.90 A˚ resolution, and reveals a high structural homology to other bacterial cyto-chromesc2. The effect of replacing the axial heme-iron methionine ligand with a lysine residue on protein structure and unfolding has been assessed using the M100K variant.

15p awards 06-04-2013 39 3   Download

The P450morsystem fromMycobacteriumsp. strain HE5, supposed to cata-lyse the hydroxylation of different N-heterocycles, is composed of three components: ferredoxin reductase (FdRmor), Fe3S4 ferredoxin (Fd mor) and cytochrome P450 (P450mor). In this study, we purified Fdmorand P450mor as recombinant proteins as well as FdRmor, which has been isolated previ-ously.

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Structural information on partially folded forms is important for a deeper understanding of the folding mechanism(s) and the factors affecting protein stabilization. The non-native compact state of equine cytochromecstabil-ized by salts in an acidic environment (pH 2.0–2.2), called the A-state, is considered a suitable model for the molten globule of cytochromec,asit possesses a native-likea-helix conformation but a fluctuating tertiary struc-ture.

11p inspiron33 23-03-2013 50 4   Download

Here, we report for the first time quinol peroxidase (QPO), an enzyme that uses ubiquinol-1 as an electron donor for the reduction of H2O2 to water. We purified QPO to 90% purity from the membrane fraction ofActino-bacillus actinomycetemcomitans. QPO is a 53.6-kDa protein that contains three heme c molecules. Theqpogene was predicted to encode a putative bacterial cytochromec peroxidase with N-terminal extensions containing an additional potential hemec-binding motif.

14p galaxyss3 21-03-2013 34 3   Download

The proteins CcmA and CcmB have long been known to be essential for cytochromec maturation inEscherichia coli. We have purified a complex of these proteins, and found it to have ATP hydrolysis activity. CcmA, which has the features of a soluble ATP hydrolysis subunit, is found in a membrane-bound complex only when CcmB is present in the membrane.

11p galaxyss3 19-03-2013 41 4   Download

Microcin J25, an antimicrobial lasso-structure peptide, induces the opening of mitochondrial permeability transition pores and the subsequent loss of cytochromec. The microcin J25 effect is mediated by the stimulation of superoxide anion overproduction. An increased uptake of calcium is also involved in this process.

9p galaxyss3 07-03-2013 39 4   Download

Cytochromec(cyto-c), added to isolated mitochondria, activates the oxida-tion of extramitochondrial NADH and the generation of a membrane potential, both linked to the activity of the cytosolic NADH/cyto-celectron transport pathway.

12p vinaphone15 28-02-2013 48 2   Download

c-Type cytochromes require specific post-translational protein systems, which vary in different organisms, for the characteristic covalent attach-ment of heme to the cytochrome polypeptide. Cytochromec biogenesis System II, found in chloroplasts and many bacteria, comprises four subun-its, two of which (ResB and ResC) are the minimal functional unit.

12p mobifone23 18-01-2013 38 4   Download

Biogenesis of cytochromec oxidase (COX) is a highly complex process involving 30 chaperones in eukaryotes; those required for the incorpora-tion of the copper and heme cofactors are also conserved in bacteria. Surf1, associated with hemeainsertion and with Leigh syndrome if defec-tive in humans, is present as two homologs in the soil bacterium Paracoc-cus denitrificans, Surf1c and Surf1q.

10p cosis54 05-01-2013 39 4   Download

Most of the biochemical and biophysical processes of proteins take place at membranes, and are thus under the influence of strong local electric fields, which are likely to affect the structure as well as the reaction mecha-nism and dynamics.

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In c-type cytochromes, heme becomes covalently attached to the polypep-tide chain by a reaction between the vinyl groups of the heme and cysteine thiols from the protein. There are two such cytochromes in mitochondria: cytochromec and cytochromec1 .

19p cosis54 09-12-2012 46 3   Download