Human UBIAD1 localizes to mitochondria and converts vitamin K(1) to vitamin K(2). Vitamin K(2) is best known as a cofactor in blood coagulation, but in bacteria it is a membrane-bound electron carrier. Whether vitamin K(2) exerts a similar carrier function in eukaryotic cells is unknown. We identified Drosophila UBIAD1/Heix as ...

The mitochondrial respiratory chain is organized within an array of supercomplexes that function to minimize the generation of reactive oxygen species during the electron transfer reactions. Structural models of supercomplexes are now known. Another recent advance is the discovery of non-OXPHOS complex proteins that appear to adhere and seal the ...

We report a highly sensitive two-photon probe (SZn2-Mito) which shows a 70-fold two-photon excited fluorescence enhancement in response to Zn(2+) and can selectively detect mitochondrial Zn(2+) in a rat hippocampal slice at a depth of 100-200 μm by using two-photon microscopy.

Mitochondrial dysfunction (primary or secondary) is detrimental to intermediary metabolism. Therapeutic strategies to treat/prevent mitochondrial dysfunction could be valuable for managing metabolic and age-related disorders. Here, we review strategies proposed to treat mitochondrial impairment. We then concentrate on redox-active agents, with mild-redox potential, who shuttle electrons among specific cytosolic or ...

Caloric restriction (CR) slows the aging process and extends longevity, but the exact underlying mechanisms remain debatable. It has recently been suggested that the beneficial action of CR may be mediated in part by adipose tissue remodeling. Mammals have two types of adipose tissue: white adipose tissue (WAT) and brown ...

The complexes of the mitochondrial respiratory chain assemble into higher-order structures called supercomplexes or respirasomes that are thought to be important in channeling electron flow and controlling ROS production. A number of recent papers identify the first protein factors necessary for supercomplex assembly and stability.

The complexes of the electron transport chain associate into large macromolecular assemblies, which are believed to facilitate efficient electron flow. We have identified a conserved mitochondrial protein, named respiratory supercomplex factor 1 (Rcf1-Yml030w), that is required for the normal assembly of respiratory supercomplexes. We demonstrate that Rcf1 stably and independently ...

Discrimination of metabolic models based on high-throughput metabolomics data, reflecting various internal and external perturbations, is essential for identifying the components that contribute to the emerging behavior of metabolic processes. Here, we investigate twelve different models of the mitochondrial electron transport chain (ETC) in Arabidopsis thaliana during dark-induced senescence in ...

The purpose of this study was to evaluate relationships between subsarcolemmal mitochondrial aggregates and electron transport chain deficiencies in skeletal muscle with the objective of establishing an association between mitochondrial accumulation and electron transport chain complex deficiency. We conducted a large-scale, retrospective study to evaluate factors associated with subsarcolemmal mitochondrial ...

Fish of the suborder Notothenioidei have successfully radiated into the Southern Ocean and today comprise the dominant fish sub-order in Antarctic waters in terms of biomass and species abundance. During evolution in the cold and stable Antarctic climate, the Antarctic lineage of notothenioids developed several unique physiological adaptations, which make ...

This work studied the effect of gossypol on the mitochondrial respiratory chain of Yarrowia lipolytica. The compound was shown to inhibit mitochondrial electron transfer and stimulate generation of reactive oxygen species. The inhibition kinetics in oxidation of various substrates (NADH, succinate, α-glycerophosphate and pyruvate + malate) by isolated mitochondria was ...

Short-chain quinones have been investigated as therapeutic molecules due to their ability to modulate cellular redox reactions, mitochondrial electron transfer and oxidative stress, which are pathologically altered in many mitochondrial and neuromuscular disorders. Recently, we and others described that certain short-chain quinones are able to bypass a deficiency in complex ...

We have previously postulated that it is possible to accidentally insert an epidural needle or catheter into the substance of the dura during attempted epidural block, creating an intradural space. It appears that injection of local anaesthetic into an intradural space leads to an initially inadequate neuraxial block but further ...

BACKGROUND:: Although infrequent, subdural block is a complication of epidural anesthesia with obvious implications. Knowledge of the spinal subdural compartment (dura-arachnoid interface) may help elucidate controversies arising from evidence that subdural catheter placement is feasible and may be difficult to identify clinically. METHODS:: Samples of arachnoid lamina obtained during in ...

The reaction of water-soluble cytochrome c (c(2)) with its physiological redox partners is facilitated by electrostatic attractions between the two protein surfaces. Using spin-labeled cytochrome c(2) from Rhodobacter capsulatus and pulse electron paramagnetic resonance (EPR) measurements we compared spatial orientation of cytochrome c(2) upon its binding to surfaces of opposite ...

The formal potential of c-type cytochromes expressed in the bacterial outer membrane was dependent on their redox state functioning in mediating extracellular electron transfer. Its negative (positive) shifting accompanying with the oxidization (reduction) of c-type cytochromes can serve to stabilize the redox states in a feedback manner.

Examining electron transfer between two proteins with identical spectroscopic signatures is a challenging task. It is supposed that several multiheme cytochromes in Shewanella oneidensis form a molecular "wire" through which electrons are transported across the cellular space and a direct study of this transient protein-protein interaction has not yet been ...

The unbinding properties of the transient complex between the electron transfer proteins azurin and cytochrome c(551) have been investigated by steered molecular dynamics simulations by pulling four different atoms of cytochrome c(551). The atoms to be pulled have been chosen to closely match the conditions of a previous experimental study ...

Various bacteria are effective in metal reduction, and there is an increasing use of such micro-organisms for decontaminating polluted environments. Iron-containing electron transfer proteins, particularly those of the cytochrome c7 family, can bind a number of toxic metals in their high oxidation states, and can reduce them via electron transfer ...

Central in respiration or photosynthesis, the cytochrome bc(1) and b(6)f complexes are regarded as functionally similar quinol oxidoreductases. They both catalyse a redox loop, the Q-cycle, which couples electron and proton transfer. This loop involves a bifurcated electron transfer step considered as being mechanistically mandatory, making the Q-cycle indispensable for ...

We have incorporated CYP3A4 (cytochrome P450 3A4) and CPR (NADPH-cytochrome P450 reductase) into liposomes with a high lipid/protein ratio by an improved method. In the purified proteoliposomes, CYP3A4 binds testosterone with Kd (app)=36±6 μM and Hill coefficient=1.5±0.3, and 75±4% of the CYP3A4 can be reduced by NADPH in the presence ...

The purple photosynthetic bacterium Rubrivivax gelatinosus has, at least, four periplasmic electron carriers, i.e., HiPIP, two cytochromes c(8) with low- and high-midpoint potentials, and cytochrome c(4) as electron donors to the photochemical reaction center. The quadruple mutant lacking all four electron carrier proteins showed extremely slow photosynthetic growth. During the ...

The first crystal structure of a ternary redox protein complex was comprised of the enzyme methylamine dehydrogenase (MADH) and two electron transfer proteins, amicyanin and cytochrome c-551i from Paracoccus denitrificans [Chen et al. Science 1994, 264, 86-90]. The arrangement of the proteins suggested possible electron transfer from the active site ...

Understanding the uncoupling at the haem active site and/or at the level of multidomain electron transfer is an important element in cytochrome P450 chemistry. Here a chimeric model system consisting of human cytochrome P450 3A4 and the soluble reductase domain of CYP102A1 from Bacillus megaterium (BMR) is used to study ...

We report the use of evanescent wave cavity ring-down spectroscopy (EW-CRDS) to monitor the reduction by ethylenediaminetetraacetic acid iron(II) complex, [FeEDTA](2-), of an adsorbed layer of oxidized cytochrome c immobilized on fused silica. The adsorption of cytochrome c at the silica-water interface was also probed using EW-CRDS and found to ...

The green photosynthetic bacterium Chloroflexus aurantiacus, which belongs to the phylum of filamentous anoxygenic phototrophs, does not contain a cytochrome bc or bf type complex which is found in all other known groups of phototrophs. This suggests that a functional replacement exists to link the reaction center photochemistry to cyclic ...

Cytochrome bc(1)-complexes of animals and bacteria (hereafter bc(1)), as well as related cytochrome b(6)f complexes of plants and cyanobacteria (hereafter bf) are dimeric quinol:cytochrome c/plastocyanin oxidoreductases capable of translocating protons across energy-converting membranes. The commonly accepted Q-cycle mechanism suggests that these enzymes oxidize two quinol molecules in their catalytic centers ...

The ubiquinol-cytochrome c oxidoreductases, central to cellular respiration and photosynthesis, are homodimers. High symmetry has frustrated resolution of whether cross-dimer interactions are functionally important. This has resulted in a proliferation of contradictory models. Here, we duplicated and fused cytochrome b subunits, and then broke symmetry by introducing independent mutations into ...

The NADPH-dependent cytochrome P450 reductase (CPR) is a key electron donor to eucaryotic cytochromes P450 (CYPs). CPR shuttles electrons from NADPH through the FAD and FMN-coenzymes into the iron of the prosthetic heme-group of the CYP. In the course of these electron transfer reactions, CPR undergoes large conformational changes. This ...

A family of five periplasmic triheme cytochromes (PpcA-E) was identified in Geobacter sulfurreducens, where they play a crucial role by driving electron transfer from the cytoplasm to the cell exterior and assisting the reduction of extracellular acceptors. The thermodynamic characterization of PpcA using NMR and visible spectroscopies was previously achieved ...

Redox-controlled backbone dynamics in cytochrome c (Cyt c) were revealed by 2D 15N NMR relaxation experiments. 15N T1 and T2 values and 1H-15N NOEs of uniformly 15N-labeled reduced and oxidized Cyt c were measured, and the generalized order parameters (S2), the effective correlation time for internal motion (taue), the 15N ...

The Rieske protein component of the cytochrome bc complex contains a [2Fe-2S] cluster ligated by two cysteines and two histidines. We report here the pK(a) values of each of the imidazole rings of the two ligating histidines (His134 and His154) in the oxidized and reduced states of the Rieske protein ...

Adrenodoxin is probably the best characterized member of the vertebrate-type [2Fe-2S]-cluster ferredoxins. It has been in the spotlight of scientific interest for many years due to its essential role in mammalian steroid hormone biosynthesis, where it acts as electron mediator between the NADPH-dependent adrenodoxin reductase and several mitochondrial cytochromes P450. ...

Ischemia damages the mitochondrial electron transport chain (ETC), mediated in part by damage generated by the mitochondria themselves. Mitochondrial damage resulting from ischemia, in turn, leads to cardiac injury during reperfusion. The goal of the present study was to localize the segment of the ETC that produces the ischemic mitochondrial ...

The heterogeneous electron-transfer (ET) reaction of cytochrome c (Cyt-c) electrostatically or covalently immobilized on electrodes coated with self-assembled monolayers (SAMs) of omega-functionalized alkanethiols is analyzed by surface-enhanced resonance Raman (SERR) spectroscopy and molecular dynamics (MD) simulations. Electrostatically bound Cyt-c on pure carboxyl-terminated and mixed carboxyl/hydroxyl-terminated SAMs reveals the same distance ...

Immunogold localization revealed that OmcS, a cytochrome that is required for Fe(III) oxide reduction by Geobacter sulfurreducens, was localized along the pili. The apparent spacing between OmcS molecules suggests that OmcS facilitates electron transfer from pili to Fe(III) oxides rather than promoting electron conduction along the length of the pili.

Selenate reductase (SER) from Thauera selenatis is a periplasmic enzyme that has been classified as a type II molybdoenzyme. The enzyme comprises three subunits SerABC, where SerC is an unusual b-heme cytochrome. In the present work the spectropotentiometric characterization of the SerC component and the identification of redox partners to ...

The formation of outer membrane (OM) cytochromes seems to be a key step in the evolution of dissimilatory iron-reducing bacteria. They are believed to be the endpoints of an extended respiratory chain to the surface of the cell that establishes the connection to insoluble electron acceptors such as iron or ...

Gluconacetobacter diazotrophicus stands out among the acetic acid bacteria as it fixes dinitrogen and is a true endophyte. It has a set of constitutive enzymes to oxidize ethanol and acetaldehyde which is upregulated during N(2)-dependent growth. The membrane-bound alcohol dehydrogenase (ADH) is a heterodimer (subunit I approximately 72 kDa, subunit ...

The cytochrome distribution in hyphal tip cells of Schizophyllum commune was visualized using resonance Raman mapping and CARS microscopy. For comparison, resonance Raman mapping and CARS imaging of cytochrome was also performed during branch formation and in completely developed central hyphae. Cytochrome, as an essential component of the electron transport ...

Metalloproteins often contain metal centers that are paramagnetic in some functional state of the protein; hence electron paramagnetic resonance (EPR) spectroscopy can be a powerful tool for studying protein structure and function. Dipolar spectroscopy allows the determination of the dipole-dipole interactions between metal centers in protein complexes, revealing the structural ...

Although Neisseria gonorrhoeae is a prolific source of eight c-type cytochromes, little is known about how its electron transfer pathways to oxygen are organized. In this study, the roles in the respiratory chain to oxygen of cytochromes c(2), c(4), and c(5), encoded by the genes cccA, cycA, and cycB, respectively, ...

Green sulfur bacteria and heliobacteria are strictly anaerobic phototrophs that have homodimeric type 1 reaction center complexes. Within these complexes, highly reducing substances are produced through an initial charge separation followed by electron transfer reactions driven by light energy absorption. In order to attain efficient energy conversion, it is important ...

Biological macromolecules involved in electron transfer reactions display chains of closely packed redox cofactors when long distances must be bridged. This is a consequence of the need to maintain a rate of transfer compatible with metabolic activity in the framework of the exponential decay of electron tunneling with distance. In ...

Recent studies have provided experimental evidence for the existence of an encounter complex, a transient intermediate in the formation of protein complexes. We use paramagnetic relaxation enhancement NMR spectroscopy in combination with Monte Carlo simulations to characterize and visualize the ensemble of encounter orientations in the short-lived electron transfer complex ...

In the cytochrome P450cam-dependent monooxygenase system from Pseudomonas putida, putidaredoxin (Pdx) shuttles electrons between putidaredoxin reductase (Pdr) and P450cam and, thus, must form transient complexes with both partners. 1-Ethyl 3-[3-(dimethylamino)propyl]carbodiimide (EDC) was found to promote formation of stoichiometric Pdr-Pdx complexes only when carboxyl groups on Pdx were activated. The yield ...

The function of cytochrome c(554) of Vibrio parahaemolyticus has not yet been determined. We have determined the physicochemical properties and crystal structure of cytochrome c(554) at 1.8 A in order to help elucidate its function. The physicochemical properties and the tertiary structure of cytochrome c(554) resemble those of dimeric cytochrome ...

BACKGROUND: Geobacter species grow by transferring electrons out of the cell--either to Fe(III)-oxides or to man-made substances like energy-harvesting electrodes. Study of Geobacter sulfurreducens has shown that TCA cycle enzymes, inner-membrane respiratory enzymes, and periplasmic and outer-membrane cytochromes are required. Here we present comparative analysis of six Geobacter genomes, including ...

Shewanella are facultative anaerobic bacteria of remarkable respiratory versatility that includes the dissimilatory reduction of metal ores. They contain a large number of multiheme c-type cytochromes that play a significant role in various anaerobic respiratory processes. Of all the cytochromes found in Shewanella, only the two most abundant periplasmic cytochromes, ...

Helicobacter pylori is a microaerophilic bacterium associated with gastric inflammation and peptic ulcers. Knowledge of how pathogenic organisms produce energy is important from a therapeutic point of view. We found d-amino acid dehydrogenase-mediated electron transport from d-proline or d-alanine to oxygen via the respiratory chain in H. pylori. Coupling of ...