redoxdependent

Redox-dependent describes processes, proteins, or interactions whose function or outcome is governed by the redox state of a system. In biology, redox state refers to the balance between oxidants and reductants, such as reactive oxygen species, NAD+/NADH, and the glutathione pool (GSH/GSSG). Redox-dependent mechanisms respond to changes in this balance and can alter enzyme activity, protein folding, signaling pathways, or gene expression.

A common mechanism is reversible oxidation of cysteine residues, which can lead to disulfide bond formation, sulfenylation, S-glutathionylation, or S-nitrosylation. These reversible modifications can change a protein’s conformation, activity, or interactions, and are often reversed as redox conditions shift back.

Examples of redox-dependent regulation include bacterial OxyR, which forms disulfide bonds in response to hydrogen peroxide to activate antioxidant genes; Rex proteins that sense the NADH/NAD+ redox state to regulate metabolism; and eukaryotic pathways such as the Nrf2-Keap1 system, as well as redox-sensitive transcription factors like AP-1 and NF-κB whose DNA-binding activity can be modulated by the cellular redox environment.

Redox-dependent processes are central to cellular signaling, stress responses, and homeostasis. Abnormal redox regulation is implicated in aging and diseases such as cancer, neurodegeneration, and inflammatory disorders. The term emphasizes the conditional nature of these processes, which rely on the cellular redox milieu rather than solely on protein sequence or structure.