Detection of a geminate photoproduct of bovine cytochrome c oxidase by time-resolved serial femtosecond crystallography.

ABSTRACT: Cytochrome c oxidase (C c O) 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, C c O has a unique binuclear center (BNC) comprised of a copper atom (Cu _B ) and a heme a ₃ iron, where O ₂ binds and is reduced to water. CO is a versatile O ₂ surrogate in ligand binding and escape reactions. Previous time-resolved spectroscopic studies of the CO complexes of bovine C c O (bC c O) revealed that photolyzing CO from the heme a ₃ iron leads to a metastable intermediate (Cu _B -CO), where CO is bound to Cu _B , before it escapes out of the BNC. Here, with a time-resolved serial femtosecond X-ray crystallography-based pump-probe method, we detected a geminate photoproduct of the bC c O-CO complex, where CO is dissociated from the heme a ₃ iron and moved to a temporary binding site midway between the Cu _B and the heme a ₃ iron, while the locations of the two metal centers and the conformation of the Helix-X, housing the proximal histidine ligand of the heme a ₃ iron, remain in the CO complex state. This new structure, combined with other reported structures of bC c O, allows the full definition of the ligand dissociation trajectory, as well as the associated protein dynamics.

SUBMITTER: Ishigami I 

PROVIDER: S-EPMC10197551 | biostudies-literature | 2023 May

REPOSITORIES: biostudies-literature