Spectroelectrochemical study of cytochrome c oxidase: pH and temperature dependences of the cytochrome potentials. Characterization of site-site interactions.

Blair, David F.; Ellis, Walther R.; Wang, H; Gray, Harry B.; Chan, Sunney I.

doi:10.1016/s0021-9258(18)67275-8

Cited by 139 publications

(63 citation statements)

References 49 publications

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“…503,504 The initial model was thus refined to include interaction with a third site, which is likely to be a copper center. 276,387,494,502 Eight different redox microstate is now required to describe the system (see Figure 21B).…”

Section: Hemes and Copper Centers Of Complex IVmentioning

confidence: 99%

“…These studies provide a full overview of the energetics of the ET processes in the respiratory chain of both aerobic organisms and those living at low O 2 levels. It is necessary to exercise caution in the interpretation of the data because the midpoint potential values of membrane proteins critically depend on external factors, such as pH, ionic strength, nature of the detergent, presence of lipids, etc. − For this reason, in addition to the pH, we also show in the following tables of redox potentials if the measurements were carried out on proteins still bound to the membrane, or on proteins extracted from the membrane using detergents. In some cases, the titrations were carried out on intact or fragments of membranous organelles, such as mitochondria, submitochondrial particles, electron transport particles, and chromatophores, that include several enzymes.…”

Section: Potentiometric Titrations Of Respiratory Membrane Proteinsmentioning

confidence: 99%

“…More thorough analyses of the UV/vis potentiometric titrations of the bovine enzyme at pH 7 consider three transitions, at 190, 260, and 340 mV with electron stoichiometries of 2, 2, and 1, respectively. , The initial model was thus refined to include interaction with a third site, which is likely to be a copper center. ,,, Eight different redox microstate is now required to describe the system (see Figure B).…”

Section: Potentiometric Titrations Of Respiratory Membrane Proteinsmentioning

confidence: 99%

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Redox Properties of the Membrane Proteins from the Respiratory Chain

Melin

Hellwig

2020

Chem. Rev.

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This review focuses on the electrochemical and spectroelectrochemical studies that gave insight into redox potentials of the four mitochondrial complexes and their homologues from bacterial respiratory chains using O2 as a terminal acceptor, thus providing crucial information about their reaction mechanism. Advantages and limitations of the use of the different techniques for the study of membrane proteins are presented. Electrocatalytic experiments are described that revealed specific features of the reaction with the substrates and inhibitors. An overview is given on the great variability of the redox and catalytic properties of the enzymes in different organisms that may be due to adaptation to the specific environments in which these enzymes function. The adaptation of the redox chain to the different types of quinone and substrates is analyzed, and future studies are discussed.

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Section: Hemes and Copper Centers Of Complex IVmentioning

confidence: 99%

Section: Potentiometric Titrations Of Respiratory Membrane Proteinsmentioning

confidence: 99%

Section: Potentiometric Titrations Of Respiratory Membrane Proteinsmentioning

confidence: 99%

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Redox Properties of the Membrane Proteins from the Respiratory Chain

Melin

Hellwig

2020

Chem. Rev.

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“…It also seems likely that ligand and internal protonation state changes near the redox centres during the catalytic cycle can affect the midpoint potentials (Wikstrom & Verkhovsky in press). It has been estimated that there are about 35-40 mV interaction energies between the redox centres, such that the reduction of any one makes it harder to reduce the others (Blair et al 1986). The same report suggests a similar interaction energy between the more distant Cu A and haem a.…”

Section: Structure Cofactor Interactions and Free Energiesmentioning

confidence: 99%

Darwin at the molecular scale: selection and variance in electron tunnelling proteins including cytochrome c oxidase

Moser

Page

Dutton

2006

Phil. Trans. R. Soc. B

101

122

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Biological electron transfer is designed to connect catalytic clusters by chains of redox cofactors. A review of the characterized natural redox proteins with a critical eye for molecular scale measurement of variation and selection related to physiological function shows no statistically significant differences in the protein medium lying between cofactors engaged in physiologically beneficial or detrimental electron transfer. Instead, control of electron tunnelling over long distances relies overwhelmingly on less than 14 A spacing between the cofactors in a chain. Near catalytic clusters, shorter distances (commonly less than 7 A) appear to be selected to generate tunnelling frequencies sufficiently high to scale the barriers of multi-electron, bond-forming/-breaking catalysis at physiological rates. We illustrate this behaviour in a tunnelling network analysis of cytochrome c oxidase. In order to surmount the large, thermally activated, adiabatic barriers in the 5-10 kcal mol-1 range expected for H+ motion and O2 reduction at the binuclear centre of oxidase on the 10(3)-10(5) s-1 time-scale of respiration, electron access with a tunnelling frequency of 10(9) or 10(10) s-1 is required. This is provided by selecting closely placed redox centres, such as haem a (6.9 A) or tyrosine (4.9 A). A corollary is that more distantly placed redox centres, such as CuA, cannot rapidly scale the catalytic site barrier, but must send their electrons through more closely placed centres, avoiding direct short circuits that might circumvent proton pumping coupled to haems a to a3 electron transfer. The selection of distances and energetic barriers directs electron transfer from CuA to haem a rather than a3, without any need for delicate engineering of the protein medium to 'hard wire' electron transfer. Indeed, an examination of a large number of oxidoreductases provides no evidence of such naturally selected wiring of electron tunnelling pathways.

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“…This functional diversity is made possible by the tuning of heme properties through heme pocket amino acid side chains that directly coordinate the heme iron or provide residues within proximity to the heme macrocycle. Residues near the heme can interact with its vinyl or propionate substituents, possibly inducing out of plane distortions. , Variations in the heme pocket architecture, including resident water molecules, have yielded a diverse family of proteins with reduction potentials that span 1 V. − Within the larger hemoprotein family, heme sensor proteins are used throughout the kingdoms of life to sense gaseous ligands, such as nitric oxide (NO), carbon monoxide (CO), and oxygen (O 2 ), and typically contain a proximal histidine ligand and, for O 2 binding proteins, have a distal pocket with hydrogen bonding residues. − …”

Section: Introductionmentioning

confidence: 99%

Heme-Edge Residues Modulate Signal Transduction within a Bifunctional Homo-Dimeric Sensor Protein

et al. 2021

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Bifunctional enzymes, which contain two domains with opposing enzymatic activities, are widely distributed in bacteria, but the regulatory mechanism(s) that prevent futile cycling are still poorly understood. The recently described bifunctional enzyme, DcpG, exhibits unusual heme properties and is surprisingly able to differentially regulate its two cyclic dimeric guanosine monophosphate (c-di-GMP) metabolic domains in response to heme gaseous ligands. Mutagenesis of heme-edge residues was used to probe the heme pocket and resulted in decreased O 2 dissociation kinetics, identifying roles for these residues in modulating DcpG gas sensing. In addition, the resonance Raman spectra of the DcpG wild type and heme-edge mutants revealed that the mutations alter the heme electrostatic environment, vinyl group conformations, and spin state population. Using small-angle X-ray scattering and negative stain electron microscopy, the heme-edge mutations were demonstrated to cause changes to the protein conformation, which resulted in altered signaling transduction and enzyme kinetics. These findings provide insights into molecular interactions that regulate DcpG gas sensing as well as mechanisms that have evolved to control multidomain bacterial signaling proteins.

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Spectroelectrochemical study of cytochrome c oxidase: pH and temperature dependences of the cytochrome potentials. Characterization of site-site interactions.

Cited by 139 publications

References 49 publications

Redox Properties of the Membrane Proteins from the Respiratory Chain

Redox Properties of the Membrane Proteins from the Respiratory Chain

Darwin at the molecular scale: selection and variance in electron tunnelling proteins including cytochrome c oxidase

Heme-Edge Residues Modulate Signal Transduction within a Bifunctional Homo-Dimeric Sensor Protein

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