Long-chain fatty acid- and acylcarnitine-bound oxygenated myoglobin interactions with outer mitochondrial membrane

Oxygenated myoglobin (oxy-Mb) releases oxygen (O₂) during interactions with the outer mitochondrial membrane (OMM) and is shown to bind hydrophobic metabolic substrates like palmitate (PLM) and palmitoylcarnitine (PLC). However, it remains unclear how the binding of these specific lipids influences oxy-Mb interaction with the OMM.

We employed molecular dynamics (MD) simulations to evaluate PLM- and PLC-bound oxy-Mb/membrane interactions in two settings: an average-composition OMM and a cardiolipin-enriched contact-site OMM (CS-OMM). Following steered MD-assisted contact establishment, we assessed unrestrained membrane-association stability and steered detachment forces.

Both PLM- and PLC-bound oxy-Mb, unrestrained after attachment to the membrane, demonstrated a strong preference for the CS-OMM, showing 2.3- to 2.7-fold increases in stability compared to the average-OMM. However, the bound lipid influenced membrane-contact persistence and resistance to steered detachment. PLM-bound oxy-Mb was 10%-20% more stable overall and required approximately twice the detachment force of the PLC-bound complex. During steered detachment, it required roughly twice the force of the PLC-bound complex and preferentially interacted with cardiolipin. Conversely, PLC-bound oxy-Mb exhibited weaker membrane association and preferentially engaged phosphatidylethanolamine and phosphatidylinositol.

The identity of the bound lipid actively modulates oxy-Mb's membrane stability, phospholipid preference, and membrane facing orientation. PLM promotes a more mechanically robust membrane association, whereas PLC produces a distinct and weaker interaction pattern. These structural differences may influence the accessibility of the heme region at the mitochondrial surface; however, O₂ release and lipid transfer were not directly measured in the present simulations.