Nature and functional implications of the cytochrome a3 transients after photodissociation of CO-cytochrome oxidase

Journal Article · Fri Mar 15 04:00:00 EST 1991 · Proceedings of the National Academy of Sciences of the United States of America; (USA)

DOI:https://doi.org/10.1073/pnas.88.6.2588· OSTI ID:5859689

Woodruff, W H; Einarsdottir, O; Dyer, R B; Bagley, K A; Palmer, G; Atherton, S J; Goldbeck, R A; Dawes, T D; Kliger, D S ^[1]

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1. Los Alamos National Laboratory, NM (USA)

Time-resolved electronic absorption, infrared, resonance Raman, and magnetic circular dichroism spectroscopies are applied to characterization of the intermediate that is formed within 20 ps after photodissociation of CO from cytochrome a3 in reduced cytochrome oxidase. This intermediate decays with the same half-life (approximately 1 microseconds) as the post-photodissociation CU+B-CO species previously observed by time-resolved infrared. The transient UV/visible spectra, kinetics, infrared, and Raman evidence suggest that an endogenous ligand is transferred from CuB to Fea3 when CO binds to CuB, forming a cytochrome a3 species with axial ligation that differs from the reduced unliganded enzyme. The time-resolved magnetic circular dichroism results suggest that this transient is high-spin and, therefore, five-coordinate. Thus we infer that the ligand from CuB binds on the distal side of cytochrome a3 and displaces the proximal histidine imidazole. This remarkable mechanistic feature is an additional aspect of the previously proposed ligand-shuttle activity of the CuB/Fea3 pair. We speculate as to the identity of the ligand that is transferred between CuB and Fea3 and suggest that the ligand shuttle may play a functional role in redox-linked proton translocation by the enzyme.

• OSTI ID: 5859689
• Journal Information: Proceedings of the National Academy of Sciences of the United States of America; (USA), Journal Name: Proceedings of the National Academy of Sciences of the United States of America; (USA) Vol. 88:6; ISSN PNASA; ISSN 0027-8424
• Country of Publication: United States
• Language: English

Related Subjects

550200* -- Biochemistry
59 BASIC BIOLOGICAL SCIENCES
ABSORPTION SPECTROSCOPY
BIOLOGICAL HALF-LIFE
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CHALCOGENIDES
CHEMICAL COMPOSITION
CHEMICAL REACTIONS
CYTOCHROME OXIDASE
CYTOCHROMES
DICHROISM
ENZYMES
HAEM DEHYDROGENASES
INFRARED SPECTRA
LIGANDS
MAGNETIC CIRCULAR DICHROISM
ORGANIC COMPOUNDS
OXIDES
OXIDOREDUCTASES
OXYGEN COMPOUNDS
PIGMENTS
PROTEIN STRUCTURE
PROTEINS
RAMAN SPECTRA
REDOX REACTIONS
SPECTRA
SPECTROSCOPY