Structural basis of mitochondrial dysfunction in response to cytochrome <i>c</i> phosphorylation at tyrosine 48.

Abstract

Regulation of mitochondrial activity allows cells to adapt to changing conditions and to control oxidative stress, and its dysfunction can lead to hypoxia-dependent pathologies such as ischemia and cancer. Although cytochrome <i>c</i> phosphorylation-in particular, at tyrosine 48-is a key modulator of mitochondrial signaling, its action and molecular basis remain unknown. Here we mimic phosphorylation of cytochrome <i>c</i> by replacing tyrosine 48 with <i>p</i>-carboxy-methyl-l-phenylalanine (<i>p</i>CMF). The NMR structure of the resulting mutant reveals significant conformational shifts and enhanced dynamics around <i>p</i>CMF that could explain changes observed in its functionality: The phosphomimetic mutation impairs cytochrome <i>c</i> diffusion between respiratory complexes, enhances hemeprotein peroxidase and reactive oxygen species scavenging activities, and hinders caspase-dependent apoptosis. Our findings provide a framework to further investigate the modulation of mitochondrial activity by phosphorylated cytochrome <i>c</i> and to develop novel therapeutic approaches based on its prosurvival effects.