Reactive cysteine thiols on microbial and host proteins (Cys-SH)

Reactive cysteine thiols are highly nucleophilic sulfhydryl groups located on specific cysteine residues within a wide array of microbial and host proteins. These residues are characterized by a significantly lowered pKa compared to standard cysteines, often due to the surrounding protein microenvironment, which facilitates their existence in the reactive thiolate form at physiological pH (PubMed: 23530071). In microbes, these thiols are essential for the activity of key enzymes such as proteases and oxidoreductases, making them vulnerable to antimicrobial electrophiles (PubMed: 29155428). In humans, they serve as critical nodes for redox signaling, enzymatic catalysis in kinases and proteases, and structural integrity through disulfide bond formation (PubMed: 21414382). Therapeutic strategies often involve covalent inhibitors that form stable bonds with these thiols, providing high potency and prolonged duration of action, though this approach requires careful design to avoid non-specific reactivity and associated toxicities (PubMed: 25698602). Because this term describes a chemical moiety found across thousands of different proteins rather than a single discrete protein, it is considered a broad target class rather than a specific therapeutic target.

Other names

Protein thiolsNucleophilic cysteinesSulfhydryl groupsRedox-active cysteinesCysteineomeProtein sulfhydryl groups

Covalent modification of the nucleophilic sulfur atom through electrophilic attack, such as Michael addition or SN2 reaction, resulting in the irreversible or slowly reversible inhibition of protein function or the modulation of redox-sensitive signaling pathways (PubMed: 25698602, PubMed: 23530071).