[Analysis of the secondary structure of the regulatory region of mRNA of the Escherichia coli rpsA gene].
The rpsA gene of E. coli coding for the ribosomal protein S1 was inserted into the plasmid pGEM-3Z under the control of a T7 promoter. The resulted plasmid was used for mRNA preparation in vitro. The toeprint analysis of the rpsA mRNA revealed a strong S1 dependence: 30S ribosomal subunits lacking S1 were inactive in the 30S initiation complex formation; addition of the free S1 restored subunits' ability to bind mRNA; a molar excess of the free S1 over ribosomes was inhibitory. The secondary structure of the rpsA mRNA in the vicinity of the initiation codon was probed with the use of specific ribonucleases. Basing on the experimental data obtained we suggest a model for the structural organisation of the rpsA mRNA translation initiation region.