Escherichia coli ribosomal 5S RNA-protein L25 nucleoprotein complex: effects of RNA binding on the protein structure and the nature of the interaction

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Abstract
The complexes of 3 variants of E. coli 5S RNA with ribosomal protein L25 were studied by high-field proton NMR. A spectroscopic method is demonstrated to help distinguish the macromolecular sources of proton resonances in nucleoprotein complexes. The effects of L25 binding on the 3 RNA tested were small; the presence of the L25 did not strongly influence the conformation of the RNA. The interaction of L25 with 5S RNA produced modest, but distinctive, alterations in the protein spectrum, in both the aromatic region and the upfield spectrum. As judged by these changes, the mechanism of binding was the same in all 3 cases. The changes seen in the spectrum of L25 indicate that its conformation is not altered in a major way upon RNA binding. Arginine residues appear to be involved in the binding mechanism. Intercalation of L25 aromatic residues with RNA bases does not appear to play a role in the interaction.