Epsilon as an initiator of translation of CAT mRNA in Escherichia coli

Epsilon sequence (UUAACUUUA) has originally been found in the bacteriophage T7 gene 10 leader region. It enhances translation in Escherichia coli via base pairing with nucleotides 458-466 located in the helical domain #17 of 16S rRNA. We have recently reported that when the complementarity to 16S rR NA is extended, the epsilon is converted from an enhancer to an independent initiator of translation. Here we report the effect of two other structura l parameters, positioning in mRNA and the degree of complementarity to 16S rRNA on the translation initiation activity of epsilon in E. coli cells. Ou r results show that E displays maximal activity as a translational initiato r at its natural 9-nucleotide-long complementarity to 16S rRNA and at a 16- nucleotide-long distance to the initiation codon. Under these conditions it s efficiency is comparable with that of the consensus Shine-Dalgarno sequen ce. (C) 2000 Academic Press.