FormylmethionyltRNAfMet

Formylmethionine, often abbreviated as fMet, is the N-formyl derivative of the amino acid methionine. It serves as the initiating amino acid in protein synthesis for many bacteria and for organelles of eukaryotic cells that retain bacterial ancestry, such as mitochondria and chloroplasts. The initiator tRNA in bacteria is tRNAiMet, which is formylated to form fMet-tRNAiMet by the enzyme methionyl-tRNA transformylase, using N10-formyltetrahydrofolate as the donor of the formyl group.

During bacterial translation initiation, the ribosome recognizes the start codon, typically AUG, with the help of the fMet-tRNAiMet, beginning the assembly of a polypeptide chain. After synthesis, the formyl group is generally removed by peptide deformylase, and in many cases the resulting N-terminal methionine is removed by methionine aminopeptidase, producing a mature protein with an N-terminal residue determined by processing.

Formylmethionine is not commonly found as a residue in mature cytosolic proteins of most eukaryotes. Its presence is a characteristic feature of bacterial gene expression and the organelles derived from bacteria. In addition to its role in translation, formylated peptides can act as chemoattractants for immune cells in animals, binding to formyl peptide receptors and influencing inflammatory responses.

Medical and research relevance includes the targeting of deformylase enzymes by antibiotics, which aim to disrupt bacterial protein maturation. Overall, formylmethionine is a key initiator in bacterial protein synthesis with implications for microbiology, immunology, and antibiotic development.