Proc Natl Acad Sci U S A. 2019 Feb 26. 116(9):
3572-3577
Izumi Ishigami,
Ariel Lewis-Ballester,
Austin Echelmeier,
Gerrit Brehm,
Nadia A Zatsepin,
Thomas D Grant,
Jesse D Coe,
Stella Lisova,
Garrett Nelson,
Shangji Zhang,
Zachary F Dobson,
Sébastien Boutet,
Raymond G Sierra,
Alexander Batyuk,
Petra Fromme,
Raimund Fromme,
John C H Spence,
Alexandra Ros,
Syun-Ru Yeh,
Denis L Rousseau.
Cytochrome c oxidase (CcO) reduces dioxygen to water and harnesses the chemical energy to drive proton translocation across the inner mitochondrial membrane by an unresolved mechanism. By using time-resolved serial femtosecond crystallography, we identified a key oxygen intermediate of bovine CcO. It is assigned to the PR-intermediate, which is characterized by specific redox states of the metal centers and a distinct protein conformation. The heme a 3 iron atom is in a ferryl (Fe4+ = O2-) configuration, and heme a and CuB are oxidized while CuA is reduced. A Helix-X segment is poised in an open conformational state; the heme a farnesyl sidechain is H-bonded to S382, and loop-I-II adopts a distinct structure. These data offer insights into the mechanism by which the oxygen chemistry is coupled to unidirectional proton translocation.
Keywords: X-ray free electron laser; bioenergetics; catalytic intermediates; complex IV; crystallography