N-Formylmethionine 3988867 206811452 2008-04-20T02:38:25Z Andyras 1144767 /* Function in protein synthesis */ terminal --> terminus {{NatOrganicBox | image= [[Image:Formylmethionine.png|270px]] | height=no | name=2-formamido-4-methylsulfanyl-butanoic acid | abbreviations=fMet | C=6 | H=11 | N=1 | O=3 | S=1 | mass=177.222 | melt_point= | density= | isoelectric_point= | dissoc_constant= | CAS= | EINECS= | PubChem=911 | SMILES=CSCCC(C(=O)O)NC=O }} '''N-Formylmethionine'''(fMet) is an [[amino acid]] found in all living [[cell (biology)|cell]]s. It is a derivative of the [[amino acid]] [[methionine]]. It is a modified form of [[methionine]] in which a [[formyl]] group has been added to methionine's [[amino]] group. It plays a crucial part in the [[protein synthesis]] of [[bacteria]], [[mitochondrion|mitochondria]] and [[chloroplast]]s. It is not used in the [[protein synthesis]] taking place in the [[cytosol]] of [[eukaryote]]s, where [[eukaryote|eukaryotic]] [[nuclear gene]]s are [[Translation (biology)|translated]]. ==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]]. N-Formylmethionine is coded by the same [[codon]] as [[methionine]], AUG. However, AUG is also the [[Translation (biology)|translation]] initiation [[codon]]. When the codon is used for initiation, N-formylmethionine 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 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]].<ref>{{GeorgiaImmunology|1/phagstep}}</ref> ==References== <references/> ==External links== * {{MeshName|N-Formylmethionine}} [[Category:Sulfur amino acids|Formylmethionine, N-]] [[Category:Molecular biology|Formylmethionine, N-]]