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

• Published in: The Journal of biological chemistry 1994-12, Vol.269 (52), p.32937-32941
• Main Authors: Reed, V S, Yang, D C
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Aspartate-tRNA Ligase - antagonists & inhibitors; Aspartate-tRNA Ligase - chemistry; Aspartate-tRNA Ligase - metabolism; Chromatography, Gel; Circular Dichroism; Humans; Molecular Sequence Data; Peptide Elongation Factor 1; Peptide Elongation Factors - metabolism; Peptides - chemistry; Peptides - metabolism; RNA, Transfer, Amino Acyl - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(20)30081-8

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.