Lorber B, Mejdoub H, Reinbolt J, Boulanger Y, Giegé R
Institut de Biologie Moléculaire et Cellulaire du Centre National de la Recherche Scientifique, Strasbourg, France.
Eur J Biochem. 1988 May 16;174(1):155-61. doi: 10.1111/j.1432-1033.1988.tb14076.x.
Cytoplasmic aspartyl-tRNA synthetase from Saccharomyces cerevisiae is a dimer made up of identical subunits of Mr 64,000 as shown by biochemical and crystallographic analyses. Previous studies have emphasized the high sensitivity of the amino-terminal region (residues 1-32) to proteolytic enzymes. This work reports the results of limited tryptic or chymotryptic digestion of the purified enzyme which gives rise to a truncated species that has lost the first 50-64 residues with full retention of both the activity and the dimeric structure. In contrast the larger tryptic fragment is distinguished from the whole enzyme by its weaker retention on heparin-substituted agarose gels. The cleaved N-terminal part presents peculiar structural features, such as a high content in lysine residues arranged in a palindromic fashion. The properties of the trypsin-modified enzyme and of the cleaved amino-terminal region are discussed in relation to the known structural characteristics of aspartyl-tRNA synthetase and of other eukaryotic aminoacyl-tRNA synthetases.
