Cellular proteins containing nucleophilic cysteine residues

Cellular proteins containing nucleophilic cysteine residues, collectively known as the 'cysteome,' represent a diverse group of proteins where specific cysteine side chains exhibit enhanced reactivity due to a lowered pKa (Backus et al., 2016, Nature). These residues are often located within functional 'hotspots' such as enzyme active sites, allosteric pockets, or protein-protein interaction interfaces, where they play critical roles in catalysis, redox-sensitive signaling, and structural stabilization (Weerapana et al., 2010, Nature). Because of their unique nucleophilicity, these cysteines are prime targets for covalent drugs that utilize electrophilic functional groups, or 'warheads,' to form irreversible or reversible chemical bonds (Resnick et al., 2019, Cell Chemical Biology). Notable examples of drugs targeting these residues include Ibrutinib, which targets Cys481 in Bruton's tyrosine kinase (BTK), and Sotorasib, which targets Cys12 in the KRAS G12C mutant (Canon et al., 2019, Nature). While targeting the cysteome allows for high potency and prolonged pharmacodynamics, it also presents significant challenges, including the risk of off-target reactivity with non-therapeutic cysteines and the potential for idiosyncratic immune responses (Lanning et al., 2014, Nature Chemical Biology). Consequently, modern drug discovery efforts focus on achieving high selectivity for specific nucleophilic cysteines to minimize systemic toxicity and improve the therapeutic index.

Other names

CysteomeCysteinomeReactive cysteinesNucleophilic cysteinesLigandable cysteines

Covalent modification of nucleophilic cysteine residues via electrophilic attack (e.g., Michael addition or SN2 reaction) by a drug's reactive moiety (warhead) to form a stable chemical adduct (Backus et al., 2016, Nature).