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.
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.
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
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.
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.
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.
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
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.
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.
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)
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.
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
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
cytochrome P450 (P450mor). In this study, we purified Fdmorand P450mor
as recombinant proteins as well as FdRmor, which has been isolated previ-ously.
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.
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
; the molecular activity or turnover number
was 12 s
at 280K in the absence of ethylene glycol. CCO
activity was studied between 240and 277 K in the presence
of ethylene glycol.
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
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.