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).