Abstract
Abstract Cytochrome c oxidase is terminal enzyme in the respiratory chain of mitochondria and many aerobic bacteria. It catalyzes reduction of oxygen to water. During its catalysis, C c O proceeds through several quite stable intermediates ( R , A , P R/M , O/O H , E/E H ). This work is concentrated on the elucidation of the differences between structures of oxidized intermediates O and O H in different C c O variants and at different pH values. Oxidized intermediates of wild type and mutated C c O from Paracoccus denitrificans were studied by means of static and time-resolved Fourier-transform infrared spectroscopy in acidic and alkaline conditions in the infrared region 1800-1000 cm -1 . No reasonable differences were found between all variants in these conditions, and in this spectral region. This finding means that the binuclear center of oxygen reduction keeps a very similar structure and holds the same ligands in the studied conditions. The further investigation in search of differences should be performed in the 4000-2000 cm -1 IR region where water ligands absorb. Abbreviations A ferrous-oxy intermediate ATR Attenuated total reflectance BG background BNC binuclear center C c O Cytochrome c oxidase E one-electron reduced intermediate F ferryl intermediate FRCO fully-reduced CO-inhibited enzyme FTIR Fourier transform infrared IR infrared NHE Normal Hydrogen Electrode N-side negatively charged side of the membrane P R/M “peroxy” intermediates; P-side positively charged side of the membrane R fully-reduced intermediate TR time-resolved WT wild type