Amino acid symbols

Symbols that stand for the amino acids, the building blocks of protein.

Each amino acid has both a three-letter symbol and a single-letter symbol.

For example, the three-letter and single-letter symbols for alanine are Ala and A.

The three-letter symbols (such as Ala) are much more widely used than the single letter ones (such as A).</P> Therefore, the following list is limited to the three-letter symbols and is further limited to those 20 alpha-amino acids specified by the genetic code: > >Alanine: Ala >Arginine: Arg >Asparagine: Asn >Aspartic acid: Asp >Cysteine: Cys >Glutamic acid: Glu >Glutamine: Gln >Glycine: Gly >Histidine: His >Isoleucine: Ile >Leucine: Leu >Lysine: Lys >Methionine: Met >Phenylalanine: Phe >Proline: Pro >Serine: Ser >Threonine: Thr >Tryptophan: Trp >Tyrosine: Tyr >Valine: Val </LI></UL> These three-letter symbols for amino acids are used not only to refer to an individual amino acid but also to present the amino acid sequence of a polypeptide or a protein.

For example, part of the sequence of insulin reads: Gly-Ile-Val-Glu-Gln-Cys-Cys-Ala-Ser-Val.

The N-terminal residue of the polypeptide or protein is by convention always on the left and the sequence reads from left-to-right toward the C-terminal residue of the polypeptide or protein.