Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Kinetics of carbon monoxide binding and electron transfer by cytochrome c polymers.

ABSTRACT: Studies on horse heart cytochrome c polymers were carried out by stopped-flow and photolysis techniques, to investigate the properties of the CO complex and the kinetics of electron transfer, mainly of the dimeric and tetrameric forms. CO binding, which does not occur with native monomers, proceeds at both pH7.0 and pH9.6, and appears to follow complex kinetics: an initial phase is observed, which is CO-concentration-dependent, followed by a very slow monomolecular phase (k~2x10(-3)s(-1) at pH7) before establishment of equilibrium. Photodissociation of the CO complex has a very low quantum yield, probably less than 0.1. Static titration data of the dimer gave an ;n' value of 0.4. These data strongly suggest heterogeneity of the population of binding sites, and have been interpreted in terms of the existence of different structures, probably owing to the non-unique type of binding of monomers during polymerization. Polymers of cytochrome c carboxymethylated on the methionine residue normally ligated to iron show simple CO recombination kinetics after photolytic removal (k(on)=1.5x10(6)m(-1).s(-1) at pH6). We therefore suggest that, for native cytochrome c, polymerization has an effect on the lability of the haem crevice, rendering the iron available for binding ligands, without, however, forming the structure of a truly open crevice. Electron transfer is, on the other hand, a simple process, and no gross differences are observed between monomer and polymers. A simple model, taking into account all these data, is suggested.

SUBMITTER: Dupre S

PROVIDER: S-EPMC1168077 | biostudies-other | 1974 Jul

REPOSITORIES: biostudies-other

ACCESS DATA

Json Xml

Similar Datasets

Single-walled carbon nanotubes alter cytochrome c electron transfer and modulate mitochondrial function.

Project description:Single-walled carbon nanotubes (SWCNTs) are broadly used for various biomedical applications such as drug delivery, in vivo imaging, and cancer photothermal therapy due to their unique physiochemical properties. However, once they enter the cells, the effects of SWCNTs on the intracellular organelles and macromolecules are not comprehensively understood. Cytochrome c (Cyt c), as a key component of the electron transport chain in mitochondria, plays an essential role in cellular energy consumption, growth, and differentiation. In this study, we found the mitochondrial membrane potential and mitochondrial oxygen uptake were greatly decreased in human epithelial KB cells treated with SWCNTs, which accompanies the reduction of Cyt c. SWCNTs deoxidized Cyt c in a pH-dependent manner, as evidenced by the appearance of a 550 nm characteristic absorption peak, the intensity of which increased as the pH increased. Circular dichroism measurement confirmed the pH-dependent conformational change, which facilitated closer association of SWCNTs with the heme pocket of Cyt c and thus expedited the reduction of Cyt c. The electron transfer of Cyt c is also disturbed by SWCNTs, as measured with electron spin resonance spectroscopy. In conclusion, the redox activity of Cyt c was affected by SWCNTs treatment due to attenuated electron transfer and conformational change of Cyt c, which consequently changed mitochondrial respiration of SWCNTs-treated cells. This work is significant to SWCNTs research because it provides a novel understanding of SWCNTs' disruption of mitochondria function and has important implications for biomedical applications of SWCNTs.

| S-EPMC3548237 | biostudies-literature

Kinetics and Energetics of Intramolecular Electron Transfer in Single-Point Labeled TUPS-Cytochrome c Derivatives.

Project description:Electron transfer within and between proteins is a fundamental biological phenomenon, in which efficiency depends on several physical parameters. We have engineered a number of horse heart cytochrome c single-point mutants with cysteine substitutions at various positions of the protein surface. To these cysteines, as well as to several native lysine side chains, the photoinduced redox label 8-thiouredopyrene-1,3,6-trisulfonate (TUPS) was covalently attached. The long-lived, low potential triplet excited state of TUPS, generated with high quantum efficiency, serves as an electron donor to the oxidized heme c. The rates of the forward (from the label to the heme) and the reverse (from the reduced heme back to the oxidized label) electron transfer reactions were obtained from multichannel and single wavelength flash photolysis absorption kinetic experiments. The electronic coupling term and the reorganization energy for electron transfer in this system were estimated from temperature-dependent experiments and compared with calculated parameters using the crystal and the solution NMR structure of the protein. These results together with the observation of multiexponential kinetics strongly support earlier conclusions that the flexible arm connecting TUPS to the protein allows several shortcut routes for the electron involving through space jumps between the label and the protein surface.

| S-EPMC8621336 | biostudies-literature

The kinetics of binding of oxygen and carbon monoxide to Gastrophilus haemoglobin.

Project description:The dimeric haemoglobin in the tracheal cells of the Gastrophilus larva was extracted and purified, and the spectral properties of its oxy- and carbon monoxide adducts are recorded. In dilute solutions the kinetic parameters of binding of oxygen and carbon monoxide were determined. In solutions between 0.1 and 50mum for oxygen k(on) is 1x10(7)m(-1).s(-1) and k(off) is 1s(-1); for carbon monoxide l(on) is 6.5x10(5)m(-1).s(-1) and l(off) is 0.14s(-1). These values are in agreement with previous equilibrium results on oxygen binding and carbon monoxide/oxygen partition. These results are discussed and compared with the known values for other monomeric protohaem proteins.

| S-EPMC1174234 | biostudies-other

Electron transfer interactome of cytochrome C.

Project description:Lying at the heart of many vital cellular processes such as photosynthesis and respiration, biological electron transfer (ET) is mediated by transient interactions among proteins that recognize multiple binding partners. Accurate description of the ET complexes - necessary for a comprehensive understanding of the cellular signaling and metabolism - is compounded by their short lifetimes and pronounced binding promiscuity. Here, we used a computational approach relying solely on the steric properties of the individual proteins to predict the ET properties of protein complexes constituting the functional interactome of the eukaryotic cytochrome c (Cc). Cc is a small, soluble, highly-conserved electron carrier protein that coordinates the electron flow among different redox partners. In eukaryotes, Cc is a key component of the mitochondrial respiratory chain, where it shuttles electrons between its reductase and oxidase, and an essential electron donor or acceptor in a number of other redox systems. Starting from the structures of individual proteins, we performed extensive conformational sampling of the ET-competent binding geometries, which allowed mapping out functional epitopes in the Cc complexes, estimating the upper limit of the ET rate in a given system, assessing ET properties of different binding stoichiometries, and gauging the effect of domain mobility on the intermolecular ET. The resulting picture of the Cc interactome 1) reveals that most ET-competent binding geometries are located in electrostatically favorable regions, 2) indicates that the ET can take place from more than one protein-protein orientation, and 3) suggests that protein dynamics within redox complexes, and not the electron tunneling event itself, is the rate-limiting step in the intermolecular ET. Further, we show that the functional epitope size correlates with the extent of dynamics in the Cc complexes and thus can be used as a diagnostic tool for protein mobility.

| S-EPMC3516563 | biostudies-literature

Protein engineering of cytochrome b562 for quinone binding and light-induced electron transfer.

Project description:The central photochemical reaction in photosystem II of green algae and plants and the reaction center of some photosynthetic bacteria involves a one-electron transfer from a light-activated chlorin complex to a bound quinone molecule. Through protein engineering, we have been able to modify a protein to mimic this reaction. A unique quinone-binding site was engineered into the Escherichia coli cytochrome b(562) by introducing a cysteine within the hydrophobic interior of the protein. Various quinones, such as p-benzoquinone and 2,3-dimethoxy-5-methyl-1,4-benzoquinone, were then covalently attached to the protein through a cysteine sulfur addition reaction to the quinone ring. The cysteine placement was designed to bind the quinone approximately 10 A from the edge of the bound porphyrin. Fluorescence measurements confirmed that the bound hydroquinone is incorporated toward the protein's hydrophobic interior and is partially solvent-shielded. The bound quinones remain redox-active and can be oxidized and rereduced in a two-electron process at neutral pH. The semiquinone can be generated at high pH by a one-electron reduction, and the midpoint potential of this can be adjusted by approximately 500 mV by binding different quinones to the protein. The heme-binding site of the modified cytochrome was then reconstituted with the chlorophyll analogue zinc chlorin e(6). By using EPR and fast optical techniques, we show that, in the various chlorin-protein-quinone complexes, light-induced electron transfer can occur from the chlorin to the bound oxidized quinone but not the hydroquinone, with electron transfer rates in the order of 10(8) s(-1).

| S-EPMC539716 | biostudies-literature

Encapsulation kinetics and dynamics of carbon monoxide in clathrate hydrate.

Project description:Carbon monoxide clathrate hydrate is a potentially important constituent in the solar system. In contrast to the well-established relation between the size of gaseous molecule and hydrate structure, previous work showed that carbon monoxide molecules preferentially form structure-I rather than structure-II gas hydrate. Resolving this discrepancy is fundamentally important to understanding clathrate formation, structure stabilization and the role the dipole moment/molecular polarizability plays in these processes. Here we report the synthesis of structure-II carbon monoxide hydrate under moderate high-pressure/low-temperature conditions. We demonstrate that the relative stability between structure-I and structure-II hydrates is primarily determined by kinetically controlled cage filling and associated binding energies. Within hexakaidecahedral cage, molecular dynamic simulations of density distributions reveal eight low-energy wells forming a cubic geometry in favour of the occupancy of carbon monoxide molecules, suggesting that the carbon monoxide-water and carbon monoxide-carbon monoxide interactions with adjacent cages provide a significant source of stability for the structure-II clathrate framework.

| S-EPMC4082632 | biostudies-literature

Electron transfer pathways in cytochrome c oxidase.

Project description:Mixed quantum mechanical/molecular mechanics calculations were used to explore the electron pathway of the terminal electron transfer enzyme, cytochrome c oxidase. This enzyme catalyzes the reduction of molecular oxygen to water in a multiple step process. Density functional calculations on the three redox centers allowed for the characterization of the electron transfer mechanism, following the sequence Cu(A)→heme a→heme a(3). This process is largely affected by the presence of positive charges, confirming the possibility of a proton coupled electron transfer. An extensive mapping of all residues involved in the electron transfer, between the Cu(A) center (donor) and the O(2) reduction site heme a(3)-Cu(B) (receptor), was obtained by selectively activating/deactivating different quantum regions. The method employed, called QM/MM e-pathway, allowed the identification of key residues along the possible electron transfer paths, consistent with experimental data. In particular, the role of arginines 481 and 482 appears crucial in the Cu(A)→heme a and in the heme a→heme a(3) electron transfer processes. This article is part of a Special Issue entitled: Allosteric cooperativity in respiratory proteins.

| S-EPMC3132828 | biostudies-literature

Functional groups modulate the sensitivity and electron transfer kinetics of neurochemicals at carbon nanotube modified microelectrodes.

Project description:The surface properties of carbon-based electrodes are critically important for the detection of biomolecules and can modulate electrostatic interactions, adsorption and electrocatalysis. Carbon nanotube (CNT) modified electrodes have previously been shown to have increased oxidative sensitivity and reduced overpotential for catecholamine neurotransmitters, but the effect of surface functionalities on these properties has not been characterized. In this study, we modified carbon-fiber microelectrodes (CFMEs) with three differently functionalized single-wall carbon nanotubes and measured their response to serotonin, dopamine, and ascorbic acid using fast-scan cyclic voltammetry. Both carboxylic acid functionalized and amide functionalized CNTs increased the oxidative current of CFMEs by approximately 2-6 fold for the cationic neurotransmitters serotonin and dopamine, but octadecylamine functionalized CNTs resulted in no significant signal change. Similarly, electron transfer was faster for both amide and carboxylic acid functionalized CNT modified electrodes but slower for octadecylamine CNT modified electrodes. Oxidation of ascorbic acid was only increased with carboxylic acid functionalized CNTs although all CNT-modified electrodes showed a trend towards increased reversibility for ascorbic acid. Carboxylic acid-CNT modified disk electrodes were then tested for detection of serotonin in the ventral nerve cord of a Drosophila melanogaster larva, and the increase in sensitivity was maintained in biological tissue. The functional groups of CNTs therefore modulate the electrochemical properties, and the increase in sensitivity from CNT modification facilitates measurements in biological samples.

| S-EPMC4169050 | biostudies-literature

Effect of steady illumination on the binding of carbon monoxide by carboxymethylated cytochrome c.

Project description:The quantum yield, [unk], is reported for the photodissociation of CO from reduced carboxymethylated cytochrome c. The values of [unk] obtained are low relative to that for myoglobin and are pH-independent, being 0.23 at pH6.1 and 0.27 at pH9.7.

| S-EPMC1177548 | biostudies-other

Electron transfer pathways in a multiheme cytochrome MtrF.

Project description:In MtrF, an outer-membrane multiheme cytochrome, the 10 heme groups are arranged in heme binding domains II and IV along the pseudo-C2 axis, forming the electron transfer (ET) pathways. Previous reports based on molecular dynamics simulations showed that the redox potential (Em) values for the heme pairs located in symmetrical positions in domains II and IV were similar, forming bidirectional ET pathways [Breuer M, Zarzycki P, Blumberger J, Rosso KM (2012) J Am Chem Soc 134(24):9868-9871]. Here, we present the Em values of the 10 hemes in MtrF, solving the linear Poisson-Boltzmann equation and considering the protonation states of all titratable residues and heme propionic groups. In contrast to previous studies, the Em values indicated that the ET is more likely to be downhill from domain IV to II because of localization of acidic residues in domain IV. Reduction of hemes in MtrF lowered the Em values, resulting in switching to alternative downhill ET pathways that extended to the flavin binding sites. These findings present an explanation of how MtrF serves as an electron donor to extracellular substrates.

| S-EPMC5358398 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data