Task: Text Categorization
Input (English): This amino acid is found on the active site of the E1, E2, and E3 enzymes involved in polyubiquitination. The domain between the L1 and L2 domains of the Insulin growth factor-Insulin receptor are rich in residues of this amino acid, while the n-acetyl modified variety of this amino acid is an antioxidant, and is used in treating acetaminophen poisoning. Compounds that are being tested to treat conditions like Chagas disease inhibit a protease with this amino acid at its active site, and those proteases are exemplified by caspases and papain. The termination codon UGA sometimes encodes for a selenium containing variant of this amino acid, which is synthesized from serine and a similarly named compound and it exists as a dimer in oxidizing environments, containing a disulfide bond. For 10 points, identify this amino acid, which, along with methionine has sulfur in its side chain.
Output (English): Science