Figure 1.

Secondary structure of the EcS8-binding site and its location on the secondary structure model of 16S rRNA. The essential nucleotides of the site are shown in bold. The three positions 597–643/641 randomized in this study and capable of forming a triple interaction are boxed. An additional possible triple involving nucleotides 594/644/645 (28) is shown. The four other covariations identified by in vitro selection for the base triple 597–643/641 are presented. The A/U-U triple requires the inverted A-U at 598–640.