Protein cysteine residues across the proteome (Cys residues)

Protein cysteine residues across the proteome, often referred to as the "cysteineome," comprise the collective set of thiol-containing amino acids that play pivotal roles in protein structure, catalysis, and regulation [1]. Due to the high nucleophilicity of the sulfur atom, these residues are susceptible to various post-translational modifications, including oxidation, nitrosylation, and palmitoylation, which serve as essential switches in redox signaling and metabolic pathways [2]. In the context of pharmacology, specific reactive cysteines are targeted by covalent drugs, such as kinase inhibitors, which utilize electrophilic "warheads" to form irreversible bonds with the target [3]. This mechanism provides enhanced selectivity and prolonged pharmacodynamics, particularly in treating cancers driven by specific mutations, such as EGFR or BTK [4]. However, the broad distribution of cysteines across thousands of proteins presents a significant challenge for drug design, as non-specific binding can lead to off-target toxicity and immunogenic responses [5]. Advances in chemoproteomics now allow for the systematic mapping of these residues to identify novel druggable pockets and assess the global selectivity of covalent ligands [1]. These residues also facilitate the formation of disulfide bonds, which are critical for the folding and stability of secreted and membrane-bound proteins [2]. Furthermore, the reactivity of specific cysteines can be modulated by their local microenvironment, making them sensitive sensors for the cellular redox state [2].

Other names

CysteineomeProteome-wide cysteinesReactive cysteinesProtein thiolsCysteine residues

Covalent modification of the cysteine thiol group via electrophilic attack (e.g., Michael addition) to form a stable, irreversible adduct [3].