translationinitiated

Translation initiated refers to the starting point of the process by which a sequence of nucleotides in messenger RNA (mRNA) is used as a template to synthesize a protein. This crucial step in gene expression occurs in the cytoplasm of the cell on ribosomes. The initiation phase involves the assembly of the ribosome on the mRNA molecule, the positioning of the initiator tRNA carrying the first amino acid, and the formation of the first peptide bond.

The process typically begins with the small ribosomal subunit binding to the mRNA. In eukaryotes, this binding often occurs at the 5' cap of the mRNA and the subunit scans along the mRNA until it encounters the start codon, which is usually AUG. In prokaryotes, the small ribosomal subunit recognizes a specific sequence called the Shine-Dalgarno sequence, located upstream of the start codon. Once the start codon is identified, the initiator tRNA, which carries methionine (or formylmethionine in prokaryotes), binds to the start codon within the ribosome's P site. Subsequently, the large ribosomal subunit joins the complex, completing the initiation machinery. This assembled complex is now ready to proceed with the elongation phase of translation, where the polypeptide chain will be extended.