Abstract
The only reliable general method currently available for determining precise higher order structure in the large ribosomal RNAs is comparative sequence analysis. The method is here applied to reveal 'tertiary' structure in the 16S-like rRNAs, i.e. structure more complex than simple double-helical, secondary structure. From a list of computer-generated potential higher order interactions within 16S rRNA one such interaction considered likely was selected for experimental test. The putative interaction involves a Watson-Crick one to one correspondence between positions 570 and 866 in the molecule (E. coli numbering). Using existing oligonucleotide catalog information several organisms were selected whose 16S rRNA sequences might test the proposed co-variation. In all of the (phylogenetically independent) cases selected, full sequence evidence confirms the predicted one to one (Watson-Crick) correspondence. An interaction between positions 570 and 866 is, therefore, considered proven phylogenetically.