Measurements of the Photodissociation Quantum Yields of MbNO and MbO<sub>2</sub> and the Vibrational Relaxation of the Six-Coordinate Heme Species

Xiong, Yue; Demidov, A.M.; Champion, P. M.

doi:10.1021/ja017359n

Cited by 132 publications

(259 citation statements)

References 49 publications

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“…Pump-probe fs experiments in the visible have determined the CO photodissociation time from the heme Fe to be Ͻ50-100 fs (2, 31) for heme excitation in the ␣-band as well as in the Soret band at 400 nm (32). Confirming CO departure dynamics based on the mid-IR differential transmission spectra is difficult because of the presence of the perturbed polarization effect.…”

Section: Differential Transmission Resultsmentioning

confidence: 99%

Direct observation of ligand transfer and bond formation in cytochrome c oxidase by using mid-infrared chirped-pulse upconversion

Treuffet

Kubarych

Lambry

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

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We have implemented the recently demonstrated technique of chirped-pulse upconversion of midinfrared femtosecond pulses into the visible in a visible pump-midinfrared probe experiment for high-resolution, high-sensitivity measurements over a broad spectral range. We have succeeded in time-resolving the CO ligand transfer process from the heme Fe to the neighboring CuB atom in the bimetallic active site of mammalian cytochrome c oxidase, which was known to proceed in <1 ps, using the full CO vibrational signature of Fe-CO bond breaking and CuB-CO bond formation. Our differential transmission results show a delayed onset of the appearance of the CuB-bound species (200 fs), followed by a 450-fs exponential rise. Trajectories calculated by using moleculardynamics simulations with a Morse potential for the CuB-C interaction display a similar behavior. Both experimental and calculated data strongly suggest a ballistic contribution to the transfer process.

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Section: Differential Transmission Resultsmentioning

confidence: 99%

Direct observation of ligand transfer and bond formation in cytochrome c oxidase by using mid-infrared chirped-pulse upconversion

Treuffet

Kubarych

Lambry

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

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“…Therefore, the geminate rebinding process appears bi-exponential for the 6c-NO-His heme proteins myoglobin and hemoglobin (35)(36)(37) and occurs with three exponential phases for the 6c-NO-His complex of NO-synthase (9) and the O 2 -sensor FixL (38), whereas it is mono-exponential for the mammalian 5c-NO sGC (10). Their kinetics are compared in Fig.…”

Section: Discussionmentioning

confidence: 99%

Molecular Basis for Nitric Oxide Dynamics and Affinity with Alcaligenes xylosoxidans Cytochrome c´

Kruglik

Lambry

Cianetti

et al. 2007

Journal of Biological Chemistry

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The bacterial heme protein cytochrome c from Alcaligenes xylosoxidans (AXCP) reacts with nitric oxide (NO) to form a 5-coordinate ferrous nitrosyl heme complex. The crystal structure of ferrous nitrosyl AXCP has previously revealed that NO is bound in an unprecedented manner on the proximal side of the heme. To understand how the protein structure of AXCP controls NO dynamics, we performed absorption and Raman timeresolved studies at the heme level as well as a molecular computational dynamics study at the entire protein structure level. We found that after NO dissociation from the heme iron, the structure of the proximal heme pocket of AXCP confines NO close to the iron so that an ultrafast (7 ps) and complete (99 ؎ 1%) geminate rebinding occurs, whereas the proximal histidine does not rebind to the heme iron on the timescale of NO geminate rebinding. The distal side controls the initial NO binding, whereas the proximal heme pocket controls its release. These dynamic properties allow the trapping of NO within the protein core and represent an extreme behavior observed among heme proteins.Nitric oxide (NO) acts as a second messenger in several physiological systems (1, 2), is involved in the production of several cytotoxic chemical species and nitrosative stress (3), and appears as an intermediate in the denitrification process (4). Cells have, thus, developed numerous heme proteins whose diverse functions involve nitric oxide binding and/or release. In some bacteria heme sensors were recently discovered (5) with a femtomolar affinity for NO, whereas cytochromes cЈ able to bind NO are found in many nitrogen-fixing, denitrifying, and photosynthetic bacteria (6). Although the physiological role the bacterial cytochrome cЈ from Alcaligenes xylosoxidans (AXCP) 2 is not yet established, the homologous cytochrome cЈ from Rhodobacter capsulatus has been shown to increase the resistance of this bacteria against NO toxicity (7,8). Thus, the bacterial cytochromes cЈ are inferred to disclose a particular behavior regarding NO dynamics and affinity. How heme proteins interact with NO and control its reactivity is ultimately related to their structure and the heme surroundings. A wide range of affinity and kinetic constants can be observed that correlates with the molecular dynamics of NO within the protein core. A striking example of this diversity is offered when comparing the NO dynamics governed by the enzyme NO synthase (9), the endogenous cellular source, and the NO receptorsoluble guanylate cyclase (10) (sGC) whose heme cofactor has a somewhat opposite role. Nitrosylated heme proteins usually form 6-coordinate complexes having histidine and NO as axial ligands at the proximal and distal sides of the heme, respectively (6c-NO-His), but some become 5-coordinate (5c) with NO (5c-NO) like sGC (11, 12) and AXCP (13,14). These latter proteins have an overall structure that presumably controls the strain upon the proximal histidine. Although sGC and AXCP possess different sequences and tertiary structures, they share the pro...

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“…The main rebinding occurs with a time constant of 8 ps; a minor (ϳ10%) ϳ50-ps phase was also observed. For comparison, in Mb a rebinding phase of ϳ5 ps was also observed, but a substantial fraction of the dissociated O 2 did not rebind on the picosecond time scale (33,(35)(36)(37). Thus, in the M80A mutant, the heme environment appeared to act as an effective "cage" not only for CO and NO but also for O 2 .…”

Section: Mutantmentioning

confidence: 94%

Ligand Dynamics in an Electron Transfer Protein

Silkstone

Jasaitis

Wilson

et al. 2007

Journal of Biological Chemistry

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Substitution of the heme coordination residue Met-80 of the electron transport protein yeast iso-1-cytochrome c allows external ligands like CO to bind and thus increase the effective redox potential. This mutation, in principle, turns the protein into a quasi-native photoactivable electron donor. We have studied the kinetic and spectral characteristics of geminate recombination of heme and CO in a series of single M80X (X ‫؍‬ Ala, Ser, Asp, Arg) mutants, using femtosecond transient absorption spectroscopy. In these proteins, all geminate recombination occurs on the picosecond and early nanosecond time scale, in a multiphasic manner, in which heme relaxation takes place on the same time scale. The extent of geminate recombination varies from >99% (Ala, Ser) to ϳ70% (Arg), the latter value being in principle low enough for electron injection studies. The rates and extent of the CO geminate recombination phases are much higher than in functional ligand-binding proteins like myoglobin, presumably reflecting the rigid and hydrophobic properties of the heme environment, which are optimized for electron transfer. Thus, the dynamics of CO recombination in cytochrome c are a tool for studying the heme pocket, in a similar way as NO in myoglobin. We discuss the differences in the CO kinetics between the mutants in terms of the properties of the heme environment and strategies to enhance the CO escape yield. Experiments on double mutants in which Phe-82 is replaced by Asp or Gly as well as the M80D substitution indicate that such steric changes substantially increase the motional freedom-dissociated CO.

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Measurements of the Photodissociation Quantum Yields of MbNO and MbO₂ and the Vibrational Relaxation of the Six-Coordinate Heme Species

Cited by 132 publications

References 49 publications

Direct observation of ligand transfer and bond formation in cytochrome c oxidase by using mid-infrared chirped-pulse upconversion

Direct observation of ligand transfer and bond formation in cytochrome c oxidase by using mid-infrared chirped-pulse upconversion

Molecular Basis for Nitric Oxide Dynamics and Affinity with Alcaligenes xylosoxidans Cytochrome c´

Ligand Dynamics in an Electron Transfer Protein

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Measurements of the Photodissociation Quantum Yields of MbNO and MbO2 and the Vibrational Relaxation of the Six-Coordinate Heme Species

Cited by 132 publications

References 49 publications

Direct observation of ligand transfer and bond formation in cytochrome c oxidase by using mid-infrared chirped-pulse upconversion

Direct observation of ligand transfer and bond formation in cytochrome c oxidase by using mid-infrared chirped-pulse upconversion

Molecular Basis for Nitric Oxide Dynamics and Affinity with Alcaligenes xylosoxidans Cytochrome c´

Ligand Dynamics in an Electron Transfer Protein

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Product

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Measurements of the Photodissociation Quantum Yields of MbNO and MbO₂ and the Vibrational Relaxation of the Six-Coordinate Heme Species