Alternative conformational states in the ribosome-associated 5.8S RNA

Two conformations of the 5.8S rRNA have been distinguished by gel electrophoresis. Diethyl pyrocarbonate and dimethyl sulphate reactivity were used to probe these conformational states in both the free molecule and those associated with 28S RNA or the ribosome. Both conformations could be demonstrated in each case and in every instance four residues, C50, A52, G53, C54, which were strongly reactive in the faster-migrating conformation were essentially unreactive in the slower-migrating form. These results suggest that the two conformations differ in the degree to which the tertiary structure is folded and raise the possibility that the 5.8S rRNA functions in translation by switching between alternative conformational states.