Complementary oligodeoxynucleotide probes of RNA conformation within the Escherichia coli small ribosomal subunit.

The large RNA molecule within each ribosomal subunit is folded in a specific and compact form. The availability of specific 16S RNA sequences on the surface of the small ribosomal subunit has been probed by using complementary oligodeoxynucleotides. The hybridization of 8-15-nucleotide-long oligomers to their RNA complements within the subunit was quantitated by using a nitrocellulose membrane filter binding assay. The probes have been grouped into classes on the basis of sequence-specific binding ability under different conditions of ionic environment, incubation temperature, and subunit activation state [as defined by the ability to bind phenylalanyl-tRNA in response to a poly(uridylic acid) message]. Oligodeoxynucleotides complementary to nucleotides flanking 7-methylguanosine residue 527 and to the 3'-terminal sequence bound 30S subunits regardless of the activation state. Oligodeoxynucleotides that complement 16S ribosomal RNA residues 1-16, 60-70, 685-696, and 1330-1339 and the sequence adjacent to the colicin E3 cleavage site at residue 1502 all bound efficiently only to subunits in an inactivated conformation. Probes complementary to residues 1-11 and 446-455 bound only inactivated subunits, and then with low efficiency. Sequences complementary to nucleotides 6-16, 99-109, 1273-1281, and 1373-1383 bound 30S subunits poorly regardless of the activation state. With one exception, each probe was bound by native or heat-denatured 16S ribosomal RNA (as determined by size-exclusion chromatography). We conclude that complementary oligodeoxynucleotide binding efficiency is a sensitive measure of the availability of specific RNA sequences under easily definable conditions.