Mutant or modified aminoacyl-tRNA synthetases (aaRS) have been used to charge non-natural amino acids to the corresponding tRNA, which incorporates them into polypeptides or proteins during recombinant synthesis. As azido homoalanine (Aha) is a structure analogue of methionine (Met), Met has been replaced effectively by Aha in proteins by the native methionyl tRNA synthetase of E. coli, [1]. A modified yeast phenylalanyl-tRNA synthetase was prepared by introduction of a T415G or T415A mutation in its α-subunit; specific residues in tryptophanyl-tRNA synthetase and methionyl-tRNA synthetase are also identified, where mutagenesis results in specificity for non-natural aminoacyl-tRNA molecules. Further developments and inventions have been done to specifically incorporate a vast number of Click components into practically any protein.
Once the azido function has been built into the protein sequence, conjugation with a large number of diverse partners including PEG-polymers, dyes, cofactors, antibodies, small molecules, toxins, additional proteins and peptides opens a wide field with many different applications from therapeutics to diagnostics.
For Incorporation of Aha by Chemical Synthesis into Peptides or other Organic Molecules the following Building Blocks are available: