Rapid electron transfer between monomers when the cytochrome bc1 complex dimer is reduced through center N

Area of Science:

• Mitochondrial respiration
• Bioenergetics
• Protein complex structure and function

Background:

• The yeast bc1 complex (cytochrome bc1) is a key enzyme in mitochondrial electron transport.
• Understanding electron transfer mechanisms within the bc1 complex is vital for elucidating cellular respiration.
• Cytochrome b subunits play a critical role in quinol oxidation and proton translocation.

Purpose of the Study:

• To investigate evidence for electron transfer between cytochrome b subunits in the yeast bc1 complex dimer.
• To analyze the kinetics and extent of cytochrome b reduction under specific inhibitory conditions.
• To elucidate the role of electron equilibration in the function of the bc1 complex.

Main Methods:

• Pre-steady state kinetic analysis of cytochrome b reduction.
• Utilizing center P inhibitors and varying concentrations of antimycin and menaquinol.
• Spectroscopic analysis (heme absorbance) to detect electron transfer.
• Kinetic modeling and simulations to interpret experimental data.

Main Results:

• Non-linear kinetics of cytochrome b reduction indicate electron equilibration between subunits.
• Evidence of inter-subunit electron transfer from uninhibited to inhibited sites.
• Kinetic models support electron equilibration between center N sites in the dimer.
• Simulations show feasible electron transfer between bH hemes via bL hemes.

Conclusions:

• Electron transfer between cytochrome b subunits in the yeast bc1 complex dimer is demonstrated.
• This inter-subunit electron transfer facilitates ubiquinol oxidation at center P.
• The process minimizes semiquinone-ferrocytochrome bH complex formation at center N.