More than 150 nucleotides flanking the initiation codon contribute to the efficiency of the ribosomal binding site from bacteriophage T7 gene 1.

The ribosomal binding site (RBS) from gene 1 of bacteriophage T7 was isolated on fragments of differing length and cloned upstream of the mouse dihydrofolate reductase gene to control the translation of its sequence. A 29 base pair sequence containing all elements generally believed to be essential for the RBS's showed extremely low activity. Additional upstream and downstream sequences were required to obtain a several orders of magnitude higher efficiency. By contrast, areas further downstream than +112 nucleotides from the initiator proved to be inhibitory, whereas the presence of an upstream RNaseIII cleavage site showed a strong stimulatory effect. This suggests that tertiary structures are involved in the function of the RBS studied. The efficient RBS's were complexed by ribosomes at much lower concentrations of the mRNA than the weak ones.