Assuntos
Aminoácidos , Proteínas do Tecido Nervoso/química , Prótons , Sequência de Aminoácidos , Isótopos de Carbono , Deutério , Escherichia coli/genética , Glutationa Transferase/metabolismo , Dados de Sequência Molecular , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/metabolismo , Isótopos de Nitrogênio , Ressonância Magnética Nuclear Biomolecular , Estrutura Secundária de Proteína , Proteínas Recombinantes de Fusão/química , Proteínas Recombinantes de Fusão/metabolismo , Sonicação , TemperaturaRESUMO
Eukaryotic aminoacyl-tRNA synthetases have dispensable extensions appended at the amino- or carboxyl-terminus as compared to their bacterial counterparts. While a synthetic peptide corresponding to the basic amino-terminal extension in yeast Asp-tRNA synthetase binds to DNA, the extension in the intact protein evidently binds to tRNA and enhances the tRNA specificity of Asp-tRNA synthetase. On the other hand, the amino-terminal extension in human Asp-tRNA synthetase, both within the intact protein and as a synthetic peptide, binds to tRNA. Here, the tRNA binding of a synthetic peptide, hKRS(Arg(25)-Glu(42)), corresponding to the amino-terminal extension of human Lys-tRNA synthetase (hKRS) was analyzed. This basic peptide bound to tRNA(Phe) and the apparent-binding constant increased with increasing concentrations of Mg(2+). The hKRS peptide also bound to DNA and polyphosphate; however, the apparent DNA-binding constants decreased at increasing concentrations of Mg(2+). The ability of the hKRS peptide to adopt alpha-helical conformation was demonstrated by NMR and circular dichroism. A Lys-rich peptide derived from the elongation factor 1alpha was also examined and bound to DNA but not to tRNA.
