Formylation of Methionine

Formylation of Methionine

Formylation of Methionine - In eukaryotes the starting N terminal amino acid is methionine . In prokaryotes methionine carries a formyl group (-CHO) and is hence called N-formylmethionine. In both prokaryotes and eukaryotes initiation of synthesis takes place through a specific methionyl tRNA called initiation tRNA. This is variously abbreviated as tRNA^met, tRNA_f^met, tRNA^fmet or tRNAi.

The initiation tRNA forms a complex with methionine in eukaryotes. This tRNA is called methionyl tRNA_f^met, Met-tRNA_f^met or, more simply, Met-tRNA_f^met.

Formyl tetrahydrofolate +	NH₂ Methionyl tRNA_f^met
Transformylase
---------------------->	N formylmethionyl tRNA_f^met

In prokaryotes an N-formyl (-CHO) group is added to the amino group of methionine to form N-formylmethionyl-tRNA_f^met (fMet tRNA^met or fMet-tRNA). This reaction is catalysed by a transformylase. The formyl group is donated by formyl tetrahydrofolate.

In prokaryotes there are two types of tRNA molecules accepting methionine, namely tRNA_f^met and tRNA_m^met only the methionine residue attached to tRNA_f^met can be formylated. Methionine residues initiating a polypeptide chain utilize tRNA_f^met. Insertion of methionine residues in internal positions of the growing polypeptide chain involves the mediation of tRNA _m^met

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Protein Synthesis Part 1 Release of Deacylated tRNA Hydrolysis of GTP Locking and Unlocking Ribosome Model inchworn Theory Conformational Changes Recognition of the Termination Signal Release of the Polypeptide Chain Prokaryote and Eukaryote Release Factors Processing Polypeptide Chain Rate of Protein Synthesis Signal Hypothesis Prokaryote and Eukaryote Protein Synthesis Teminism

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