N-Formylmethionine

N-Formylmethionine (fMet) is a derivative of the amino acid methionine in which a formyl group has been added to the amino group. It is specifically used by bacteria, mitochondria, and plastids for the initiation of protein synthesis. The presence of N-formylmethionine is one of the factors that differentiate bacterial proteins from those of eukaryotes and archaea, which start with methionine.

Structure and Properties

N-Formylmethionine is a peptide that contains a formyl group attached to the amino group of methionine. The formyl group is derived from formic acid, with the formula HCOOH. The presence of this group gives N-formylmethionine unique properties, such as a higher hydrophobicity compared to methionine.

Role in Protein Synthesis

In bacteria, mitochondria, and plastids, protein synthesis begins with the aminoacyl-tRNA carrying N-formylmethionine (fMet-tRNA^fMet) recognizing the start codon (usually AUG) on the mRNA. This is facilitated by the initiation factor IF2 (in bacteria) or IF2/IF3 (in mitochondria and plastids). The fMet-tRNA^fMet then forms a complex with the ribosome, allowing the addition of the next amino acid and the formation of the first peptide bond.

Clinical Significance

The presence of N-formylmethionine in bacterial proteins makes it a target for the immune system. Some antibiotics, such as daptomycin, work by binding to fMet-tRNA^fMet and preventing the initiation of protein synthesis. Additionally, the detection of N-formylmethionine can be used as a diagnostic tool for bacterial infections.

See Also

• Protein biosynthesis
• Translation (biology)
• Methionine
• Formyl group