Electron transfer pathways in cytochrome c oxidase

Abstract

Mixed quantum mechanical/molecular mechanics calculations, were used to explore the electron pathway of the terminal electron transfer enzyme, Cytochrome c Oxidase. This enzyme catalyzes the reduction of molecular oxygen to water in a multiple step process. Density functional calculations on the three redox centers allowed for the characterization of the electron transfer mechanism, following the sequence CuA → heme a → heme a3. This process is largely affected by the presence of positive charges, confirming the possibility of a proton coupled electron transfer. An extensive mapping of all residues involved in the electron transfer, between the CuA center (donor) and the O2 reduction site heme a3-CuB (receptor), was obtained by selectively activating/deactivating different quantum regions. The method employed, called QM/MM e-pathway, allowed the identification of key residues along the possible electron transfer paths, consistent with experimental data. In particular, the role of arginines 481 and 482 appears crucial in the CuA → heme a and in the heme a → heme a3 electron transfer processes.

The histone H3-H4 tetramer is a copper reductase enzyme

“…How the tetramer extracts electrons from a reducing co-factor(s) is unclear, as is the location at which this occurs. Electrons could transfer directly to the tetramer-bound copper from co-factors or through the protein in a mechanism involving a chain of residues in transient redox states (Lucas et al, 2011;Williams et al, 1997). In this regard, whether the sequence differences between the histone H3 variants or post-translational modifications of the histones influence the kinetic properties or co-factor requirements of the H3-H4 tetramer enzyme activity remain interesting and open questions.…”

Electron transfer in proteins: theory, applications and future perspectives

“…A two-step mechanism between CuA and haem a 3 -CuB via haem a is generally accepted. 92,94 Several pathways, however, have been proposed. Following the tunnelling currents method Medvedev et al found two possible paths.…”

Fe3+-Sensitive Carbon Dots for Detection of Fe3+ in Aqueous Solution and Intracellular Imaging of Fe3+ Inside Fungal Cells

“…As the most abundant transition metal in cellular systems, iron with its chemical versatility plays indispensable roles in physiological processes (Gao R. et al, 2019) such as oxygen transport (Aisen et al, 1999), electron transfer (Lucas et al, 2011), and enzymatic catalysis (Eisenstein, 2000). Excess or deficiency will cause damages to live systems (Bischof et al, 2019).…”