Structural insights into functional properties of the oxidized form of cytochrome c oxidase

• Published in: Nature communications Vol. 14; no. 1; p. 5752
• Main Authors: Ishigami, Izumi, Sierra, Raymond G., Su, Zhen, Peck, Ariana, Wang, Cong, Poitevin, Frederic, Lisova, Stella, Hayes, Brandon, Moss, Frank R., Boutet, Sébastien, Sublett, Robert E., Yoon, Chun Hong, Yeh, Syun-Ru, Rousseau, Denis L.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 16.09.2023; Nature Publishing Group; Nature Portfolio
• Subjects: 140/133; 631/45/535/1266; 631/45/607; 631/57/1464; Biological membranes; Cell Membrane; Chemical energy; Crystallography; Crystallography, X-Ray; Cytochrome; Cytochrome-c oxidase; Cytochromes; Electron transport; Electron Transport Complex IV; Enzymes; Heme; Humanities and Social Sciences; Iron; Membranes; multidisciplinary; Oxidase; Oxygen; Protons; Raman spectroscopy; Reduction; Resonance; Science; Science (multidisciplinary); Spectroscopy; Structure-function relationships; Translocation; Water chemistry; X-ray crystallography
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-023-41533-x

Cytochrome c oxidase (C c O) is an essential enzyme in mitochondrial and bacterial respiration. It catalyzes the four-electron reduction of molecular oxygen to water and harnesses the chemical energy to translocate four protons across biological membranes. The turnover of the C c O reaction involves an oxidative phase, in which the reduced enzyme (R) is oxidized to the metastable O H state, and a reductive phase, in which O H is reduced back to the R state. During each phase, two protons are translocated across the membrane. However, if O H is allowed to relax to the resting oxidized state (O), a redox equivalent to O H , its subsequent reduction to R is incapable of driving proton translocation. Here, with resonance Raman spectroscopy and serial femtosecond X-ray crystallography (SFX), we show that the heme a 3 iron and Cu B in the active site of the O state, like those in the O H state, are coordinated by a hydroxide ion and a water molecule, respectively. However, Y244, critical for the oxygen reduction chemistry, is in the neutral protonated form, which distinguishes O from O H , where Y244 is in the deprotonated tyrosinate form. These structural characteristics of O provide insights into the proton translocation mechanism of C c O. Using resonance Raman spectroscopy and serial femtosecond X-ray crystallography, the authors show the heme a 3 iron and Cu B in the resting oxidized form of Cytochrome c Oxidase are coordinated by a hydroxide ion and a water molecule, respectively.