Topography of rna in the ribosome localization of the 16 s rna 5' end by immune electron microscopy

The location of the 5′ end of 16 S RNA on the 30 S subunit has been determined. This has been done using immune electron microscopy of the 30 S subunits reconstituted from the 16 S RNA carrying 2,4-dinitrophenyl-hapten at its 5′-terminal phosphate group. Triphenylphosphine/2,2′-dipyridyl disulfide and 2,4-dinitrophenyl-ethylenediamine have been used as condensing and nucleophilic reagents, respectively, for modification of 16 S RNA. The reaction proceeds rapidly in mild conditions and results in a high yield of the modified RNA. Thus, a new general procedure for labeling the 5′-terminal nucleotides of high molecular weight RNAs is described. The 5′ end of 16 S RNA has been found to be located on a “lower” one-third of the small ribosomal subunit, on the side opposite to the ledge (platform).