N-Formylmethionine
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| Names | |
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| IUPAC name
2-Formylamino-4-methylsulfanylbutanoic acid
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| Other names
2-Formylamino-4-methylsulfanyl-butyric acid
Formylmethionine N-Formyl(methyl)homocysteine | |
| Identifiers | |
3D model (JSmol)
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| EC Number |
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PubChem CID
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| Properties | |
| C6H11NO3S | |
| Molar mass | 177.22 g/mol |
| Supplementary data page | |
| N-Formylmethionine (data page) | |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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N-Formylmethionine (fMet) is a proteinogenic amino acid found in Bacteria and related Eukaryotic organelles. It is a derivative of the amino acid methionine in which a formyl group has been added to the amino group. It is specifically used for initiation of protein synthesis, and may be removed after.
fMet plays a crucial part in the protein synthesis of bacteria, mitochondria and chloroplasts. It is not used in cytosolicprotein synthesis of eukaryotes, where eukaryotic nuclear genes are translated. It is also not used by Archaea.
Function in protein synthesis
fMet is a starting residue in the synthesis of proteins in prokaryotes and, consequently, is located at the N-terminus of the growing polypeptide. fMet is delivered to the ribosome (30S) - mRNA complex by a specialized tRNA (tRNA.fMet) which has a 5'-CAU-3' anticodon that is capable of binding with the AUG start codon located on the mRNA.
fMet is coded by the same codon as methionine, AUG. However, AUG is also the translation initiation codon. When the codon is used for initiation, fMet 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. Many organisms use variations of this basic mechanism.
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.
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 fMet 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
External links
- N-Formylmethionine at the U.S. National Library of Medicine Medical Subject Headings (MeSH)