Myoglobin-Membrane Association Facilitates Oxygen Release via Active-Site Tuning

Area of Science:

• Biochemistry
• Molecular Biology
• Cellular Respiration

Background:

• Myoglobin (Mb) is a heme protein vital for oxygen (O2) transport in muscle.
• Mitochondria require a steady O2 supply for efficient energy production.
• Understanding Mb-membrane interactions is key to cellular oxygen homeostasis.

Purpose of the Study:

• To investigate how oxymyoglobin (MbO2) interaction with a model outer mitochondrial membrane affects its oxygen affinity.
• To elucidate the molecular mechanisms underlying changes in MbO2 oxygen release kinetics upon membrane binding.

Main Methods:

• UV-visible and Resonance Raman spectroscopy to probe heme site structure.
• Stopped-flow kinetics to measure oxygen release rates.
• Classical and QM/MM simulations to model molecular interactions.

Main Results:

• Spectroscopic studies revealed subtle structural changes in the Mb heme binding site upon interaction with liposomes.
• Kinetic measurements showed a 2-fold increase in the rate constant for O2 release from MbO2.
• Simulations indicated proximal effects and heme plane distortions drive increased O2 dissociation.

Conclusions:

• Membrane association induces conformational changes in Mb, facilitating O2 release.
• This mechanism potentially enhances oxygen availability to mitochondria.
• Fine-tuning of Mb active site conformation optimizes mitochondrial function and energy production.