N-terminus

By convention, peptide sequences are written N-terminus to C-terminus, left to right (in LTR writing systems).

Amino acids link to one another by peptide bonds which form through a dehydration reaction that joins the carboxyl group of one amino acid to the amine group of the next in a head-to-tail manner to form a polypeptide chain.

It often contains signal peptide sequences, "intracellular postal codes" that direct delivery of the protein to the proper organelle.

The N-terminal amino acid of a protein is an important determinant of its half-life (likelihood of being degraded).

Modifications include the removal of initiator methionine (iMet) by aminopeptidases, attachment of small chemical groups such as acetyl, propionyl and methyl, and the addition of membrane anchors, such as palmitoyl and myristoyl groups[3] N-terminal acetylation is a form of protein modification that can occur in both prokaryotes and eukaryotes.

The N-terminus can also be modified by the addition of a fatty acid anchor to form N-acetylated proteins.

A tetrapeptide (example: Val - Gly - Ser - Ala ) with green highlighted N-terminal α-amino acid (example: L- valine ) and blue marked C-terminal α-amino acid (example: L- alanine ). This tetrapeptide could be encoded by the mRNA sequence 5'- GUU GGU AGU GCU -3'.