MAJOR IDENTITY ELEMENT OF GLUTAMINE TRANSFER-RNAS FROM BACILLUS-SUBTILIS AND ESCHERICHIA-COLI IN THE REACTION WITH BACILLUS-SUBTILIS GLUTAMYL-TRANSFER-RNA SYNTHETASE

Early investigations revealed that Bacillus subtilis glutamyl-tRNA syn thetase [GluRS (bs)] is responsible for aminoacylating both glutamate tRNA [tRNA(Glu) (bs)] and glutamine tRNA [tRNA(Gln) (bs)] with glutama te. The same Bacillus enzyme can also efficiently attach glutamate to one isoacceptor glutamine tRNA [tRNA(1)(Gln) (ec)] of Escherichia coil in vitro but not to tRNA(2)(Gln) (ec) and tRNA(Glu) (ec). To characte rize identity elements of these glutamine tRNAs in the interaction wit h GluRS (bs), tRNA(2)(Gln) (ec), tRNA(1)(Gln) (ec), three other mutant glutamine tRNAs [tRNA(2)(Gln) (AU) (C34 --> U34), tRNA(2)(Gln) (12M) (C34 --> U34, 31A-U39 --> 31U-A39), and tRNA(2)(Gln) (M21) (64C --> G5 0 --> 64G-C50, 63U-A51 --> 63A-U51)] originated from tRNA(2)(Gln) (ec) , tRNA(Gln) (bs), and a mutant tRNA(M)(Gln) (bs) whose U at the 34th p osition (U34), was replaced to C (C34), were produced in E. coli. All of the E. coli glutamine tRNAs containing U34 such as tRNA(1)(Gln), tR NA(2)(Gln) (AU), and tRNA(2)(Gln) (12M) could be charged with glutamat e by GluRS (bs), whereas tRNA(2)(Gln) (ec) and its T-stem mutant tRNA( Glu) (M21) containing C34 could not be charged by the same enzyme. The unique change of C34 to U34 of tRNA(2)(Gln) (ec) acquired glutamate a cceptor activity by GluRS (bs). This result suggests that the U34 is t he major identity element of tRNA(1)(Gln) (ec) in the recognition by G luRS (bs). The same situation was found in tRNA(Gln) (bs). The glutama te acceptor activity of tRNA(Gln) (bs) disappeared on replacement of U 34 to C34. To find out whether modified bases in tRNA(Gln) (bs) are in volved in the recognition by GluRS (bs), glutamylation of tRNA(Gln) (b s) produced by in vitro transcription was also examined but the ill vi tro transcript of tRNA(Gln) (bs) could not be charged with glutamic ac id by GluRS (bs). All of these mean that the major recognition element for GluRS (bs) is U at the 34th position of both tRNA(Gln) (bs) and t RNA(1)(Gln) (ec) as a modified form.