Fig. 4. Specificity of tRNA charging of T.thermophilus AspRSs and archaeal P.kodakaraensis AspRS and effect of the L1 loop on tRNA discrimination. (A) Aspartylation levels (plateau values) of unfractionated T.thermophilus tRNA with AspRS-1 or AspRS-2 and with native or mutated AspRS from Pyrococcus. (B) Identification by hybridization assays of tRNAAsp (a) and tRNAAsn (b) aspartylated by the various AspRSs. The AspRS mutant from P.kodakaraensis has the L1 loop exchanged by that from Thermus AspRS-2; C, control with uncharged tRNA.