Photodissociated cytochrome c oxidase

cryotrapped metastable intermediates

Massimo Sassaroli, Yuan Chin Ching, Pramod V. Argade, Denis L. Rousseau

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

By freezing CO-bound cytochrome c oxidase at cryogenic temperatures, we have been able to cryotrap metastable intermediates of photodissociation. The differences in the resonance Raman spectrum between these intermediates and ligand-free reduced cytochrome oxidase at cryogenic temperatures are the same as those between the phototransient and the fully reduced preparation detected with 10-ns excitation at room temperature. The largest difference occurs in the iron-histidine stretching mode of cytochrome a3, which shifts by up to 8 cm-1 to higher frequency in the photoproduct. At 4 K the iron-histidine mode displays two unrelaxed frequencies in the photoproduct, which we attribute to two different unrelaxed structures of the heme pocket. The frequencies and intensities of the lines in the resonance Raman spectrum are sensitive to the incident laser power density in both the ligand-free fully reduced preparation and the photoproduct even at 4 K. At 77 K the carbonyl stretching mode of the formyl group in cytochrome a32+ is especially sensitive to laser power, displaying two frequencies-1666 cm-1 at low-flux density and 1674 cm-1 at high-flux density. These frequencies may reflect a change in conformation of the formyl group or a change in its interaction with the protein such as in hydrogen bonding to the carbonyl of the formyl group. The absence of immediate relaxation of the CO photoproduct must be considered when one studies the structure and kinetics of the O2 intermediates that are formed in triple trapping and flow-flash experiments followine photodissociation of the CO-bound enzyme.

Original languageEnglish (US)
Pages (from-to)2496-2502
Number of pages7
JournalBiochemistry®
Volume27
Issue number7
StatePublished - 1988
Externally publishedYes

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Electron Transport Complex IV
Carbon Monoxide
Photodissociation
Histidine
Cryogenics
Stretching
Temperature
Raman scattering
Cytochromes a3
Lasers
Iron
Fluxes
Ligands
Hydrogen Bonding
Cytochromes
Heme
Freezing
Conformations
Hydrogen bonds
Display devices

ASJC Scopus subject areas

  • Biochemistry

Cite this

Sassaroli, M., Ching, Y. C., Argade, P. V., & Rousseau, D. L. (1988). Photodissociated cytochrome c oxidase: cryotrapped metastable intermediates. Biochemistry®, 27(7), 2496-2502.

Photodissociated cytochrome c oxidase : cryotrapped metastable intermediates. / Sassaroli, Massimo; Ching, Yuan Chin; Argade, Pramod V.; Rousseau, Denis L.

In: Biochemistry®, Vol. 27, No. 7, 1988, p. 2496-2502.

Research output: Contribution to journalArticle

Sassaroli, M, Ching, YC, Argade, PV & Rousseau, DL 1988, 'Photodissociated cytochrome c oxidase: cryotrapped metastable intermediates', Biochemistry®, vol. 27, no. 7, pp. 2496-2502.
Sassaroli, Massimo ; Ching, Yuan Chin ; Argade, Pramod V. ; Rousseau, Denis L. / Photodissociated cytochrome c oxidase : cryotrapped metastable intermediates. In: Biochemistry®. 1988 ; Vol. 27, No. 7. pp. 2496-2502.
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