A 2ND PUTATIVE MESSENGER-RNA BINDING-SITE ON THE ESCHERICHIA-COLI RIBOSOME

Translation in bacteria is initiated by a base-pairing interaction bet ween the extreme 3'-end of the small-subunit rRNA and a purine-rich do main (Shine-Dalgarno (SD) sequence) preceding the initiation codon at the 5'-end of most bacterial mRNAs. Here, we describe the identificati on of a second functional and alternative site on the Escherichia coli ribosome which is capable of interacting with mRNA devoid of SD seque nces and initiate the translation. This site is localized between nt 1 340 and 1360 of the 16S rRNA in E. coli and is complementary to the un translated region at the 5'-end of tobacco mosaic virus RNA (Omega seq uence).