RESUMO
A unique transfer RNA (tRNA)/aminoacyl-tRNA synthetase pair has been generated that expands the number of genetically encoded amino acids in Escherichia coli. When introduced into E. coli, this pair leads to the in vivo incorporation of the synthetic amino acid O-methyl-l-tyrosine into protein in response to an amber nonsense codon. The fidelity of translation is greater than 99%, as determined by analysis of dihydrofolate reductase containing the unnatural amino acid. This approach should provide a general method for increasing the genetic repertoire of living cells to include a variety of amino acids with novel structural, chemical, and physical properties not found in the common 20 amino acids.
Assuntos
Escherichia coli/genética , Código Genético , Metiltirosinas/metabolismo , Biossíntese de Proteínas , RNA de Transferência de Tirosina/metabolismo , RNA de Transferência/metabolismo , Tirosina-tRNA Ligase/metabolismo , Anticódon , Códon/genética , Códon/metabolismo , Códon de Terminação , Escherichia coli/crescimento & desenvolvimento , Escherichia coli/metabolismo , Espectrometria de Massas , Mathanococcus/enzimologia , Mathanococcus/genética , Mutação , RNA Bacteriano/genética , RNA Bacteriano/metabolismo , RNA de Transferência/genética , RNA de Transferência de Tirosina/genética , Supressão Genética , Aminoacilação de RNA de Transferência , Transformação Bacteriana , Tirosina-tRNA Ligase/química , Tirosina-tRNA Ligase/genéticaRESUMO
The efficient synthesis of a water-soluble C11a-epi-analogue (6b) of quinocarcin is described. This substance, and a netropsin amide conjugate (8) lack the capacity to inflict oxidative damage on DNA due to the stereoelectronic geometry of their oxazolidine nitrogen atoms. The capacity of these substances to alkylate DNA through the generation of an iminium species has been examined. Both compounds were found to be unreactive as DNA alkylating agents. The results of this study are discussed in the context of previous proposals on the mode of action of this family of antitumor alkaloids.
