N-Formylmethionine

N-Formylmethionine(fMet) is an amino group.

It plays a crucial part in the protein synthesis of bacteria, translated.

Function in protein synthesis

fMet is a starting residue in the synthesis of tRNA (tRNA.fMet) which has a 5'-CAU-3' anticodon that is capable of binding with the AUG start codon located on the mRNA.

N-Formylmethionine is coded by the same codon as methionine is used. Many organisms use variations of this basic mechanism.

The addition of the formyl group to methionine is catalyzed by the aminoacyl-tRNA synthetase.

Note that methionine can be loaded either onto tRNA.fMet or tRNA.Met. Transformylase will catalyze the addition of the formyl group to methionine only if methionine has been loaded onto tRNA.fMet and NOT onto tRNA.Met.

Relevance to immunology

Because N-Formylmethionine is present in proteins made by prokaryotes but not in those made by eukaryotes, the immune system can use it to help distinguish self from non-self. Polymorphonuclear cells can bind proteins starting with N-Formylmethionine, and use them to initiate phagocytosis.^[1]

References

1. ^ Immunology at MCG 1/phagstep