Cysteine residue in protein

Cysteine residues are the sulfur-containing amino acid building blocks present within proteins. They are unique due to their thiol (-SH) side chain, which is chemically reactive and can undergo various post-translational modifications, including oxidation to form disulfide bonds (cystine), S-glutathionylation, S-nitrosylation, and conjugation with metals (as seen in zinc fingers)[1][2][4][5][6]. Disulfide bonds formed between cysteine residues greatly stabilize protein tertiary and quaternary structures in the oxidizing extracellular environment, contribute to protein rigidity, and can be essential for biological activity[1][3][4][5]. Cysteine's thiol group also acts as a nucleophile in many enzyme active sites (such as proteases, oxidoreductases), making such cysteines targets for regulation by redox changes or for covalent inhibition by some drugs[2][6][7]. Post-translational modifications of cysteine are major mediators of redox-sensing and signal transduction, especially in response to oxidative stress[6][7]. These modifications can reversibly or irreversibly alter protein function, and dysregulation is implicated in diseases such as diabetes, cancer, and neurodegeneration[2][6]. Cysteine residues themselves, however, are not considered a drug target; instead, specific proteins containing catalytically or structurally important cysteines can be, making “cysteine residues in proteins” an incorrect designation for a canonical therapeutic target.

Other names

Cys residueprotein cysteinecysteinyl residue

Covalent modification of cysteine thiols (inhibition or activation of enzyme activity) - Disulfide bond reduction/oxidation - Alteration of redox signaling