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Crystal structure of CO-bound cytochrome c oxidase determined by serial femtosecond X-ray crystallography at room temperature

By Izumi Ishigami, Nadia Zatsepin1, Masahide Hikita2, Chelsie E Conrad1, Garrett Charles Nelson1, Jesse David Coe1, Shibom Basu1, Thomas D. Grant, Matthew H. Seaberg, Raymond G. Sierra, Mark S. Hunter3, Petra Fromme1, Raimund Fromme, Syun-Ru Yeh, Denis L. Rousseau

1. Arizona State University 2. Albert Einstein College of Medicine 3. SLAC National Accelerator Laboratory

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Category

BioXFEL Publications

Published on

Type

journal-article

Author

Izumi Ishigami and Nadia A. Zatsepin and Masahide Hikita and Chelsie E. Conrad and Garrett Nelson and Jesse D. Coe and Shibom Basu and Thomas D. Grant and Matthew H. Seaberg and Raymond G. Sierra and Mark S. Hunter and Petra Fromme and Raimund Fromme and Syun-Ru Yeh and Denis L. Rousseau

Citation

Ishigami, I. et al., 2017. Crystal structure of CO-bound cytochrome c oxidase determined by serial femtosecond X-ray crystallography at room temperature. Proceedings of the National Academy of Sciences, p.201705628. Available at: http://dx.doi.org/10.1073/pnas.1705628114.

Abstract

Cytochromecoxidase (CcO), the terminal enzyme in the electron transfer chain, translocates protons across the inner mitochondrial membrane by harnessing the free energy generated by the reduction of oxygen to water. Several redox-coupled proton translocation mechanisms have been proposed, but they lack confirmation, in part from the absence of reliable structural information due to radiation damage artifacts caused by the intense synchrotron radiation. Here we report the room temperature, neutral pH (6.8), damage-free structure of bovine CcO (bCcO) in the carbon monoxide (CO)-bound state at a resolution of 2.3 Å, obtained by serial femtosecond X-ray crystallography (SFX) with an X-ray free electron laser. As a comparison, an equivalent structure was obtained at a resolution of 1.95 Å, from data collected at a synchrotron light source. In the SFX structure, the CO is coordinated to the hemea3iron atom, with a bent Fe–C–O angle of ∼142°. In contrast, in the synchrotron structure, the Fe–CO bond is cleaved; CO relocates to a new site near CuB, which, in turn, moves closer to the hemea3iron by ∼0.38 Å. Structural comparison reveals that ligand binding to the hemea3iron in the SFX structure is associated with an allosteric structural transition, involving partial unwinding of the helix-X between hemeaanda3, thereby establishing a communication linkage between the two heme groups, setting the stage for proton translocation during the ensuing redox chemistry.

DOI

http://dx.doi.org/10.1073/pnas.1705628114

Funding

NSF-STC Biology with X-ray Lasers (NSF-1231306)