Synonyms: L-2-Amino-4-(methylthio)butyric acid
CAS No.: 63-68-3
Molecular Formula: C5H11NO2S
Molecular Weight: 149.21
Methionine (abbreviated as Met or M; encoded by the codon AUG) is an α-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated −NH3+ form under biological conditions), an α-carboxylic acid group (which is in the deprotonated −COO− form under biological conditions), and an S-methyl thioether side chain, classifying it as a non-polar, aliphatic amino acid. It is essential in humans, meaning the body cannot synthesize it and thus it must be obtained from the diet.
Methionine is coded for by the initiation codon meaning it indicates the start of the coding region and is the first amino acid produced in a nascent polypeptide during mRNA translation. and is coded by the initiation codon AUG, which also indicates mRNA's coding region where translation into protein begins.