ESCHERICHIA-COLI GLUTAMINYL-TRANSFER RNA-SYNTHETASE .2. CHARACTERIZATION OF THE GLNS GENE-PRODUCT

  • 1 January 1982
    • journal article
    • research article
    • Vol. 257  (19) , 1644-1650
Abstract
Glutaminyl-tRNA synthetase was purified by a simple, 2-column procedure from an E. coli K12 strain carrying the glnS structural gene on plasmid pBR322. The primary sequence of this enzyme as derived from the DNA sequence was confirmed. Manual Edman degradation was used to identify the NH2-terminal sequence of the protein. Oligopeptides scattered throughout the primary sequence of glutaminyl-tRNA synthetase were sequenced by the gas chromatographic-mass spectrometric method and matched to the theoretical peptides derived from the translated DNA sequence. The expected carboxyl terminus at position 550 was verified by carboxypeptidase B digestion. The primary sequence of glutaminyl-tRNA synthetase contains no extensive sequence repeats. A search was made for sequence homologies between this enzyme and the few other aminoacyl-tRNA synthetases for which primary sequences are available. A single homologous region was shared by at least 3 of the synthetases examined [i.e., E. coli tyrosyl tRNA synthetase, alanyl tRNA synthetase and tryptophanyl tRNA synthetase].