2000 – Sidney M. Hecht

Peptide and Protein Analogues Containing Synthetic Amino Acids at Defined Positions

The information that specifies the structure of the proteins utilized in living organisms is encoded in their DNA. The decoding process involves several intermediate species, notably messenger RNAs and transfer RNAs, the latter of which are ordinarily activated uniquely with their cognate amino acids. The fidelity of this activation process is both extraordinary and absolutely essential for the elaboration of proteins containing the intended amino acid at each position. By the use of messenger RNAs, containing unique codons at predetermined sites and intentionally misacylated transfer RNAs, we have been able to prepare proteins containing synthetic amino acids at predetermined positions, i.e., we have increased the number of building blocks that can be used to assemble protein structures. This will be illustrated in the lecture by the formation of analogues of firefly luciferase that emit light of altered wavelength.

We have also used misacylated tRNAs to inquire about the ability of the peptide bond-forming apparatus to catalyze the formation of modified peptide-like linkages that do not normally occur in nature. This will be illustrated by consideration of a ribosome-mediated nucleophilic displacement reaction.