The proton pump of the mitochondrial bc1 complex

Area of Science:

• Biochemistry
• Molecular Biology
• Bioenergetics

Background:

• The precise molecular mechanism underlying the proton pump activity of the respiratory chain bc1 complex is not fully elucidated.
• A long-standing hypothesis suggests a cooperative linkage between protonation/deprotonation events in the complex's apoproteins and the redox reactions at the quinone catalytic center.
• Protolytic residues within the apoproteins are proposed to facilitate proton transfer pathways between bulk aqueous phases and the redox center.

Purpose of the Study:

• To investigate the role of specific subunits within the bc1 complex in the proton pump process.
• To review recent experimental evidence supporting the involvement of polypeptide carboxyl residues in the proton pump mechanism.
• To identify specific residues critical for proton pump function.

Main Methods:

• Review of experimental data from studies on purified bovine and P. denitrificans bc1 enzymes.
• Analysis of the role of polypeptide carboxyl residues in proton transfer.
• Investigation of specific enzyme subunits, including the Rieske Fe/S protein.

Main Results:

• Experimental evidence has confirmed a significant role for polypeptide carboxyl residues in the proton pump mechanism.
• Studies utilizing both bovine and P. denitrificans purified enzymes have pinpointed a specific involvement of aspartic acid residue(s).
• These aspartic acid residues are located within the Rieske Fe/S protein and are implicated in the proton pump function.

Conclusions:

• Polypeptide carboxyl residues play a definite role in the proton pump mechanism of the bc1 complex.
• Aspartic acid residue(s) within the Rieske Fe/S protein are specifically involved in the proton pump function.
• These findings contribute to understanding the molecular basis of proton translocation in respiratory chains.