Characterization of a novel N-terminal peptide in human aspartyl-tRNA synthetase. Roles in the transfer of aminoacyl-tRNA from aminoacyl-tRNA synthetase to the elongation factor 1 alpha.
The kinetics of the N-terminal 32 residue-deleted human aspartyl-tRNA synthetase (hDRS delta 32) was analyzed. The kinetics of aspartyl-adenylate formation and Asp-tRNA synthesis by hDRS delta 32 were indistinguishable from those of hDRS. However, the dissociation of Asp-tRNA from hDRS delta 32 was much faster than that of hDRS. Unlike hDRS delta 32-catalyzed aspartylation of tRNA was not affected by the elongation factor 1 alpha. Two N-terminal peptides of hDRS, hDRS(T5-E26) and hDRS(D12-R27), were synthesized. Both peptides bind to tRNA-Sepharose. Both peptides, hDRS(T5-E26) and hDRS(D12-R27), are monomeric and oligomerize at high peptide concentration or in 50% propylene glycol. The peptide hDRS(T5-E26) showed little alpha-helical content as analyzed by CD spectroscopy, while hDRS(D12-R27) showed appreciable alpha-helical contents in nonpolar solvents. These results suggest that the N terminus in hDRS may mediate the slow release of Asp-tRNA and facilitate the interaction of the hDRS.Asp-tRNA complex with the elongation factor 1 alpha. The demonstration of alpha-helix formation of the hDRS N-terminal peptide is consistent with the hypothetical amphiphilic helix of the N-terminal extension in hDRS. A model for the transfer of Asp-tRNA from hDRS to elongation factor 1 alpha is presented.
Reed
V S
VS
Department of Chemistry, Georgetown University, Washington, District of Columbia 20057.
Yang
D C
DC
D000595:Amino Acid Sequence; D001226:Aspartate-tRNA Ligase / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D002850:Chromatography, Gel; D002942:Circular Dichroism; D006801:Humans; D008969:Molecular Sequence Data; D020648:Peptide Elongation Factor 1; D010445:Peptide Elongation Factors / Q000378:metabolism*; D010455:Peptides / Q000737:chemistry / Q000378:metabolism*; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism*
D020648:Peptide Elongation Factor 1; D010445:Peptide Elongation Factors; D010455:Peptides; D012346:RNA, Transfer, Amino Acyl; D001226:Aspartate-tRNA Ligase