Michiel Lodder

Tandemly Activated tRNAs as Participants in Protein Synthesis

While all studies of protein synthesis to date have employed monoaminoacylated transfer RNAs, there have been reports that bisphenylalanyl-tRNA is formed by Thermus thermophilus phenylalanyl-tRNA synthetase. Such tandemly activated tRNAs have now been prepared by chemicoenzymatic techniques and are shown to function in both prokaryotic and mammalian protein synthesizing systems. They exhibit characteristics consistent with their possible utility under extreme conditions in natural systems and have important potential advantages for protein elaboration in cell free systems. Mechanistically, the bisaminoacylated tRNAs bind to the ribosomal A-site and utilize the aminoacyl moiety attached to the 3′-position of the terminal adenosine for addition to the growing polypeptide chain. Following translocation to the P-site and transfer of the formed peptidyl moiety, the donor tRNA dissociates from the ribosome as a monoaminoacylated tRNA capable of functioning in a subsequent polypeptide elongation step.

N-substituted 2-amino-4-pentenoic acids for amino acid protection and resolution

Abstract N-Substituted 2-amino-4-pentenoic acid derivatives employed for the protection of racemic amino acids were shown to be capable of permitting the chromatographic separation of R and S isomers. When Nα was disubstituted with benzyl and phenylfluorenyl groups, the racemic amino acids could be separated with facility on open silica gel columns. Further, the optically pure N-protected amino acids so derived could be used for the preparation of misacylated suppressor transfer RNAs.