1. Detection of a Geminate Photoproduct of Bovine Cytochrome c Oxidase by Time-Resolved Serial Femtosecond Crystallography
- Author
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Ishigami, Izumi, Carbajo, Sergio, Zatsepin, Nadia, Hikita, Masahide, Conrad, Chelsie E, Nelson, Garrett, Coe, Jesse, Basu, Shibom, Grant, Thomas, Seaberg, Matthew H, Sierra, Raymond G, Hunter, Mark S, Fromme, Petra, Fromme, Raimund, Rousseau, Denis L, and Yeh, Syun-Ru
- Subjects
Inorganic Chemistry ,Chemical Sciences ,Acquired Cognitive Impairment ,Brain Disorders ,Cattle ,Animals ,Electron Transport Complex IV ,Oxidation-Reduction ,Copper ,Ligands ,Oxygen ,Crystallography ,X-Ray ,Iron ,Water ,General Chemistry ,Chemical sciences ,Engineering - Abstract
Cytochrome c oxidase (CcO) is a large membrane-bound hemeprotein that catalyzes the reduction of dioxygen to water. Unlike classical dioxygen binding hemeproteins with a heme b group in their active sites, CcO has a unique binuclear center (BNC) composed of a copper atom (CuB) and a heme a3 iron, where O2 binds and is reduced to water. CO is a versatile O2 surrogate in ligand binding and escape reactions. Previous time-resolved spectroscopic studies of the CO complexes of bovine CcO (bCcO) revealed that photolyzing CO from the heme a3 iron leads to a metastable intermediate (CuB-CO), where CO is bound to CuB, before it escapes out of the BNC. Here, with a pump-probe based time-resolved serial femtosecond X-ray crystallography, we detected a geminate photoproduct of the bCcO-CO complex, where CO is dissociated from the heme a3 iron and moved to a temporary binding site midway between the CuB and the heme a3 iron, while the locations of the two metal centers and the conformation of Helix-X, housing the proximal histidine ligand of the heme a3 iron, remain in the CO complex state. This new structure, combined with other reported structures of bCcO, allows for a clearer definition of the ligand dissociation trajectory as well as the associated protein dynamics.
- Published
- 2023