In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.

The final step in this compound's biosynthesis requires the action of O-acetylserine lyase, and the N-acetylated form of this compound is used to treat acetominophen overdoses. This amino acid is prenylated in Rab escort protein, and it also recieves a radical from a tyrosine residue in the mechanism of ribonucleotide reductase. A "knot" of these residues is present in TGF-beta, and the E1 ubiquitin-activating enzymes contain one of these residues in the active site. Two of these residues and two histidines coordinate zinc in the zinc finger motif, and with glycine and glutamate it forms the peptide glutathione. A derivative of this amino acid is present in the active site of glutathione peroxidase, this amino acids' "seleno-" variety. It is also responsible for stabilizing tertiary structure by forming disulfide bonds. FTP, name this amino acid with a thiol side chain, with one-letter abbreviation C.
Science