Reacting to reductive stress at the mitochondrial import gate.

A byproduct of mitochondrial energy production is the generation of reactive oxygen species (ROS). Too much ROS is toxic, but ROS deficiency is equally deleterious (reductive stress). In a recent study, McMinimy et al. uncovered a ubiquitin proteasome-mediated mechanism at the translocase of the outer membrane (TOM) complex, which senses ROS depletion and adjusts mitochondrial protein import accordingly.