[The Thermus thermophilus 5S rRNA-protein complex: Identifications of specific binding sites for proteins L5 and L18 in 5S rRNA]. / 5S rRNK-belkovyi kompleks Thermus thermophilus. Opredelenie spetsificheskikh uchastkov sviazyvaniia belkov L5 i L18 na 5S rRNK.

Three 5S rRNA-binding ribosomal proteins (L5, L18, TL5) of extremely thermophilic bacterium Thermus thermophilus have earlier been isolated. Structural analysis of their complexes with rRNA requires identification of their binding sites in the 5S rRNA. Previously, a TL5-binding site has been identified, a TL5-RNA complex crystallized, and its structure determined to 2.3 A. The sites for L5 and L18 were characterized, and two corresponding 5S rRNA fragments constructed. Of these, a 34-nt fragment specifically interacted with L5, and a 55-nt fragment interacted with L5, L18, and with both proteins. The 34-nt fragment-L5 complex was crystallized; the crystals are suitable for high-resolution X-ray analysis.

RNA-binding properties of an unusual ribosomal protein TL5 from Thermus thermophilus.

The gene encoding the 5S rRNA-binding ribosomal protein TL5 from Thermus thermophilus, an extremely thermophilic species, was expressed in E. coli. A method for isolation of TL5 from the overproducing strain was developed. Samples of TL5 protein isolated from ribosomes and the overproducing strain displayed identical RNA-binding properties. Circular dichroic spectroscopy was used to calculate the secondary structure of the protein. TL5 was shown to form a stable complex with the 3'-terminal fragment of 5S rRNA, which is similar to the fragment of E. coli RNA that binds to L25 protein. The data suggest that TL5 from T. thermophilus and L25 from E. coli bind to similar sites on the 5S rRNA molecule.