Chain Elongation

Chain Elongation

Chain Elongation - Elongation of the polypeptide chain requires elongation factors (EF). These are EP-Tu, EP-Ts and EF-G in prokaryotes and EF-l and EF-2 in eukaryotes.

a. The second amino acid tRNA complex (aa₂ tRNA) now occupies the A site. There is enzymatic recognition of internal codons. The process requires EF- Tu, GTP and Mg++

b. Formation of a peptide bond takes place by transfer off Met to the second amino acid (aa₂) Mg++ and K+ are required. The catalyzing enzyme is peptidyl transferase.

c. Translocation. The aa₂ tRNA complex moves from the A site to the P site. This process is caned translocation and requires EP.G, GTP and Mg++. Translocation involves movement of the ribosome relative to mRNA in the 5'-->3' direction. The tRNA molecule off Met is unloaded from the ribosome. The third amino acid tRNA complex (aa₃ tRNA) now occupies the vacant P site

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