Dissected antiporter modules establish minimal proton-conduction elements of the respiratory complex I

Area of Science:

• Biochemistry
• Biophysics
• Structural Biology

Background:

• Respiratory Complex I is a vital proton pump for cellular energy production.
• The precise mechanisms of its long-range energy transduction remain incompletely understood.
• Understanding Complex I is crucial for deciphering fundamental bioenergetic processes.

Purpose of the Study:

• To investigate the proton-conducting capabilities of engineered minimal modules derived from bacterial Complex I.
• To elucidate the functional roles of specific structural elements in Complex I's proton transport.
• To provide experimental evidence for the modular nature of Complex I's energy transduction.

Main Methods:

• Engineering and dissecting minimal proton-conducting membrane modules from bacterial Complex I.
• Utilizing a combination of biophysical, biochemical, and computational experiments.
• Reconstituting engineered modules into proteoliposome membranes to assess proton conduction.

Main Results:

• Isolated antiporter-like modules of Complex I possess all necessary elements for proton conduction across membranes.
• Proton conduction rates are regulated by conformational changes in buried ion-pairs, influenced by electric field effects.
• Bulky residues within proton channels play a critical role in coupling proton transport to the enzyme's machinery.

Conclusions:

• Individual antiporter modules of Complex I are experimentally validated as the functional units responsible for proton transport.
• Electrostatic and conformational coupling mechanisms are highlighted as key drivers of modular energy transduction in Complex I.
• These findings offer insights into conserved mechanisms across various energy-transducing enzymes.