Membrane surface geometry is a determinant of mitochondrial electron transfer and cellular adaptation

Abstract

Energy conversion in living organisms relies on biological membranes that facilitate electron transfer between oxidoreductases. In mitochondria, this process is mediated by the electron transport chain embedded in the inner mitochondrial membrane (IMM). Under various physiological and genetic conditions, mitochondrial matrix Na+ levels increase, reducing IMM fluidity through the formation of ternary coordination adducts between Na+ and phospholipids. These adducts impair ubiquinone (CoQ) transfer between respiratory complexes, thereby promoting mitochondrial reactive oxygen species (mtROS) production and activating the hypoxic adaptive pathway. Here, we show that modifying solely the ionic subatomic interaction with phospholipids is sufficient to prevent initiation of this pathway. Compound A (CA) outcompetes Na+ for phospholipid binding without impairing CoQ transfer, thereby preventing mtROS production and hypoxic adaptation. This divergence arises from the penta-coordinate complexes formed by CA with phospholipids, in contrast to the trigonal adducts formed by Na+. This structural distinction preserves IMM fluidity because CA:phospholipid assemblies adopt a less angular configuration. These findings establish membrane-surface geometry, modulated by ion:phospholipid interactions, as an unexpected determinant of membrane biology, mitochondrial energy conversion, redox signalling, and cellular adaptation, with profound implications for physiology and disease.