Asparaginyl-tRNA synthetase from Escherichia coli has significant sequence homologies with yeast aspartyl-tRNA synthetase

The Escherichia coli asnS gene codes for asparaginyl-tRNA synthetase (NRSEC). We have sequenced the asnS region, including 382 bp of the 5'-untranslated region, 1398 bp of the coding region and 280 bp of the 3'-untranslated region. The DNA-derived NRSEC amino acid (aa) sequence was confirmed by direct aa sequencing of the N-terminal parts of the native protein and of a 28-kDa internal fragment generated by trypsin digestion. The asnS gene product has been purified to homogeneity using three chromatographic steps. Sequence comparison of the deduced NRSEC sequence with all aminoacyl-tRNA synthetase sequences showed significant homologies with the yeast aspartyl-tRNA synthetase and weaker relationships with other aminoacyl-tRNA synthetases for aa with an XAX codon.