Lipid-mediated Protein-protein Interactions Modulate Respiration-driven ATP Synthesis

Area of Science:

• Biochemistry
• Membrane biophysics
• Bioenergetics

Background:

• Membrane-bound proton transporters are crucial for biological energy conversion.
• Proton electrochemical gradients power ATP synthesis via ATP synthase.
• Cytochrome bo3 (ubiquinol oxidase) acts as a proton pump.

Purpose of the Study:

• To investigate the impact of lipid composition on ATP synthesis driven by co-reconstituted proton pump and ATP synthase.
• To understand the role of protein density and lipid interactions in respiratory chain activity.

Main Methods:

• Co-reconstitution of cytochrome bo3 and ATP synthase into liposomes.
• Systematic variation of liposome lipid composition (DOPC with DOPA, DOPE, DOPG, cardiolipin).
• Measurement of ATP synthesis rates under varying lipid compositions and protein densities.

Main Results:

• ATP synthesis rates significantly decreased with increasing fractions of anionic/non-bilayer lipids (DOPA, DOPE, DOPG, cardiolipin).
• A 5% addition of DOPG reduced ATP synthesis by nearly 50% in 100 nm liposomes.
• Increased distance between proteins abolished lipid dependence, indicating proton transfer along the membrane at high protein densities.

Conclusions:

• Proton transfer between cytochrome bo3 and ATP synthase occurs along the membrane, dependent on local protein density.
• Lipid-dependent modulation of protein-protein interactions may regulate respiratory chain activity.
• Cellular regulation of respiratory chain function can be achieved through lipid-mediated control of protein complex interactions.