Fig. 1.

Key components of the PMRS. Diverse antioxidants protect the cell under stress conditions, including ascorbate at the hydrophilic cell surface and both CoQ and α-tocopherol in the hydrophobic phospholipid bilayer. Both NADH-b5R reductase and NQO1 act at the PM to reduce CoQ. These two enzymes contribute to the PMRS, providing the electrons that are required to maintain its antioxidant properties. NADH-AFR reductase, a trans-oriented activity shows a strong dependency on the CoQ status of the PM, and NQO1 also contribute to the PMRS and are responsive to oxidative stress and aging (29, 58).