Localization of 3' ends of 5S and 23S rRNAs in reconstituted subunits of Escherichia coli ribosomes.

Periodate-oxidized 3' ends of 5S, 23S, and 16S rRNAs from Escherichia coli were allowed to react with fluorescein thiosemicarbazide, then labeled rRNAs were reconstituted into active ribosomal subunits. The fluorescein moiety on each of the rRNAs when reconstituted into ribosomal subunits was accessible to anti-fluorescein IgG as determined by fluorescence quenching and by sucrose gradient centrifugation. The region at which an antibody molecule bond to the labeled ribosomal subunits was determined by immunoelectron microscopy. The 3' end of the 5S RNA was localized on the central protuberance of the 50S subunit. The corresponding region for the 3' end of the 23S RNA was below the stalk on the noninterfacing surface. The 3' end of the 16S RNA was localized to the upper edge of the large lobe of 30S subunits, as reported previously.