The Template Theory and the Role of Transpeptidation in Protein Biosynthesis

Abstract

The synthesis of protein occurs without detectable evidence of free peptide intermediates. This fact, and the specificity of proteins, have been explained by the so-called ‘template theory’, in which it is assumed that the amino-acids are laid down in their correct order on a template (? consisting of nucleic acid) with subsequent bond formation and separation from the template¹. Recent work has shown that transpeptidation occurs with peptides in artificial systems², and evidence has been sought for the participation of transpeptidation in protein synthesis. In these experiments protein synthesis has been brought about in the presence of isotopically labelled amino-acid. The resultant protein is degraded, the appropriate amino-acid isolated from two different parts of the chain and the specific activities compared. It is assumed that if thetemplate theory is correct, all amino-acids must be laid down on the template effectively simultaneously, so that differences in activity of the same amino-acid residue in different parts of the chain are evidence for transpeptidation³. We wish to show that this assumption is not necessarily justifiable.