It is specifically used for initiation of protein synthesis from bacterial and organellar genes, and may be removed post-translationally . fMet plays a crucial part in the protein synthesis of bacteria, mitochondria and chloroplasts.
Why is fMet required for protein synthesis?
fMet is required for efficient initiaiton of protein synthesis in most groups of bacteria. The 30S ribosome–mRNA complex specifically recruits tRNAs with a formylated amino acid – tRNA fMet attached to fMet in the natural case.
Why do bacteria start with a fMet residue instead of a methionine?
Because the fMet directs initiation, proteins in bacteria start ( N -terminus) with a fMet residue instead of a methionine. Further occurrences of the "AUG" codon will result in a normal methionine, because a normal "elongating" tRNA Met is used.
