Practice question

In prokaryotes, initiator tRNA is first aminoacylated with methionine then formylated at alpha-amino group by methionyl-tRNA formyltransferase using formyl-tetrahydrofolate as donor, generating N-formyl-methionine. Formylation blocks free amino terminus ensuring it can only form peptide bond as donor at N-terminus, establishing directionality, and enhances binding to IF2 and P site with higher initiation efficiency. After nascent chain emergence, peptide deformylase removes formyl group and methionine aminopeptidase may excise methionine, revealing mature N-terminus for many cytosolic proteins. This refined regulation supports accurate ribosomal assembly, quality control and translational fidelity under diverse physiological conditions and growth states.