Long range RNA-RNA interactions in the 30 S ribosomal subunit of E. coli.

We have attempted to identify long-range interactions in the tertiary structure of RNA in the E. coli 30 S ribosome. Native subunits were cleaved with ribonuclease and separated into nucleoprotein fragments which were deproteinized and fractionated into multi-oligonucleotide complexes under conditions intended to preserve RNA-RNA interactions. The final products were denatured by urea and heat and their constituent oligonucleotides resolved and sequenced. Many complexes contained complementary sequences known to be bound together in the RNA secondary structure, attesting to the validity of the technique. Other co-migrating oligonucleotides, not joined in the secondary structure, contained mutually complementary sequences in locations that allow base-pairing interaction without disrupting pre-existing secondary structure. In seven instances the complementary relationship was found to have been preserved during phylogenetic diversification.