Protonation-State-Dependent Communication in Cytochrome c Oxidase

Area of Science:

• Biochemistry
• Molecular Biology
• Biophysics

Background:

• Cytochrome c oxidase is crucial for cellular respiration, acting as both a redox enzyme and proton pump.
• Proton transfer to the binuclear redox center (BNC) is essential for its function and occurs via D- and K-channels.
• Regulation of proton transfer is vital for enzyme function and proton pumping across membranes.

Purpose of the Study:

• To investigate the protonation-state-dependent interplay between the D- and K-channels in cytochrome c oxidase.
• To elucidate the role of specific residues, K362 and N139, in regulating proton transfer pathways.
• To understand the gating mechanism of proton flow through the D-channel.

Main Methods:

• Utilized molecular dynamics simulations.
• Examined 16 different protonation state combinations of key residues in the D- and K-channels.
• Analyzed communication pathways, positional correlations, and hydrogen-bonded networks.

Main Results:

• The K-channel's influence on the D-channel is dependent on residue protonation states.
• Protonation of K362 affects the strength and means of communication within the channels.
• Residue N139 acts as a gate, its conformation influenced by D-channel and K362 protonation, thereby regulating proton passage.

Conclusions:

• Proton transfer regulation in cytochrome c oxidase involves intricate channel communication.
• Residue K362 plays a key role in modulating channel interactions and proton transfer efficiency.
• N139's gating function facilitates or hinders proton flow based on specific protonation states, impacting enzyme activity.