Diverse off-target cysteine- and zinc-binding proteins

Diverse off-target cysteine- and zinc-binding proteins represent a heterogeneous collection of proteins that are unintentionally modified by drugs, particularly those containing electrophilic warheads or metal-chelating groups. Cysteine-reactive off-targets often include highly abundant proteins with hyper-reactive nucleophilic thiols, such as Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and Glutathione S-transferases (GSTs), which can lead to metabolic disruption or impaired antioxidant defenses when inhibited (Lanning et al., Nature Chemical Biology 2014). Zinc-binding off-targets encompass a vast array of proteins, including zinc-finger transcription factors and various hydrolases, where drugs may displace the structural or catalytic zinc ion, resulting in protein instability or loss of function (Pace & Weerapana, Biomolecules 2014). These interactions are a major concern in drug development as they are frequently associated with idiosyncratic toxicities, hepatotoxicity, and reduced therapeutic windows for covalent inhibitors and metalloenzyme ligands. Understanding the reactivity and accessibility of these sites across the proteome is critical for improving drug selectivity and minimizing safety risks in clinical candidates (Backus et al., Nature 2016).

Other names

Cysteine-reactive proteomeZinc-binding proteomeOff-target electrophile-binding proteinsNucleophilic cysteine residuesZinc-ejecting targets

Drugs interact with these proteins through covalent modification of nucleophilic cysteine thiol groups (e.g., via Michael addition) or through the coordination and potential displacement of essential zinc ions in structural or catalytic sites (Backus et al., Nature 2016; Pace & Weerapana, Biomolecules 2014).