Ultrafast and not-so-fast dynamics of cytochrome oxidase: the ligand shuttle and its possible functional significance

William H. Woodruff; R. Brian Dyer; Oloef Einarsdottir; Kristen A. Peterson; Page O. Stoutland; K. A. Bagley; Graham Palmer; Jon R. Schoonover; David S. Kliger; Robert A. Goldbeck; Timothy D. Dawes; Jean-Louis Martin; J.-C. Lambry; Stephen J. Atherton; Stefan M. Hubig

doi:10.1117/12.44219

1 June 1991 Ultrafast and not-so-fast dynamics of cytochrome oxidase: the ligand shuttle and its possible functional significance

William H. Woodruff, R. Brian Dyer, Oloef Einarsdottir, Kristen A. Peterson, Page O. Stoutland, K. A. Bagley, Graham Palmer, Jon R. Schoonover, David S. Kliger, Robert A. Goldbeck, Timothy D. Dawes, Jean-Louis Martin, J.-C. Lambry, Stephen J. Atherton, Stefan M. Hubig

Author Affiliations +

Proceedings Volume 1432, Biomolecular Spectroscopy II; (1991) https://doi.org/10.1117/12.44219
Event: Optics, Electro-Optics, and Laser Applications in Science and Engineering, 1991, Los Angeles, CA, United States

Abstract

Time-resolved electronic absorption, infrared, resonance Raman, and magnetic circular dichroism spectroscopies are applied to characterization of the intermediate which is formed within 20 ps after photodissociation of CO from cytochrome a3 of reduced cytochrome oxidase. This intermediate decays with the same halflife (ca. 1 microsecond(s)) as the post- photodissociation CuB+-CO species previously observed by time-resolved infrared. The transient UV-Vis 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 which 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 it is inferred 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. The authors suggest that the ligand shuttle may play a functional role in redox-linked proton translocation by the enzyme. More detail on this work is presented elsewhere.

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William H. Woodruff, R. Brian Dyer, Oloef Einarsdottir, Kristen A. Peterson, Page O. Stoutland, K. A. Bagley, Graham Palmer, Jon R. Schoonover, David S. Kliger, Robert A. Goldbeck, Timothy D. Dawes, Jean-Louis Martin, J.-C. Lambry, Stephen J. Atherton, and Stefan M. Hubig "Ultrafast and not-so-fast dynamics of cytochrome oxidase: the ligand shuttle and its possible functional significance", Proc. SPIE 1432, Biomolecular Spectroscopy II, (1 June 1991); https://doi.org/10.1117/12.44219

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