Download n-formyl methionine

N-Formylmethionine
Formylmethionine (fMet) is an amino acid found in all living cells. It is a derivative of the amino acid methionine. It
is a modified form of methionine in which a formyl group has been added to methionine's amino group. It plays a
crucial part in the protein synthesis of bacteria, mitochondria and chloroplasts. It is not used in the protein
synthesis taking place in the cytosol of eukaryotes, where eukaryotic nuclear genes are translated. fMet is a
starting residue in the synthesis of proteins in prokaryotes and, consequently, is located at the N-terminus of the
growing polypeptide. N-Formylmethionine is coded by the same codon as methionine, AUG. However, AUG is also
the translation initiation codon. When the codon is used for initiation, N-formylmethionine is used instead of
methionine, thereby forming the first amino acid of the nascent peptide chain. When the same codon appears
later in the mRNA, normal methionine is used. The addition of the formyl group to methionine is catalyzed by the
enzyme transformylase. This modification is done after methionine has been loaded onto tRNA. fMet by
aminoacyl-tRNA synthetase.