In vivo and in vitro transcription of the Escherichia coli glutaminyl-tRNA synthetase gene.

We have characterized the in vivo and in vitro transcription products of the Escherichia coli glnS gene which codes for the enzyme glutaminyl-tRNA synthetase. The in vivo glnS transcript is about 1.9 kilobases long. Sequence analysis of the 5'- and 3'-ends of glnS mRNA showed that transcription initiates approximately 30 bases upstream from the translation initiation codon AUG and terminates approximately 230 bases downstream from the termination codon UAA. Characterization of the in vitro transcripts of glnS revealed similar transcription initiation and termination sites as were found in the glnS mRNA produced in vivo. These results indicate that the Pribnow box structure upstream and the dyad symmetry terminator structure downstream of the glnS structural region are regulatory signals used for glnS expression. In vitro transcription of glnS is not autogenously regulated by glutaminyl-tRNA synthetase and glutamine; it is also not affected by the presence of tRNA.