Evidence on the conformation of HeLa-cell 5.8 S rRNA during interaction with 28 S rRNA

The sites and extents of bisulphite-mediated deamination of cytidine residues in HeLa-cell 5.8 S rRNA within the 5.8 S / 28 S rRNA complex have been determined. Comparison of these data with equivalent data for isolated ('unbound') 5.8 S rRNA suggests that the conformation of several cytidine residues, including inter alia those within the 5'- and 3'-terminal sequences, differs in the two forms of 5.8 S rRNA. We therefore conclude that the sequences comprising stem 'a' of the isolated 5.8 S rRNA are involved in hydrogen-bonding to 28 S rRNA in the 60 S ribosomal subunit, but that the interactions are more subtle and complex than those proposed in earlier models.