The Thermus thermophilus 5S rRNA-protein complex: Identification of specific binding sites for proteins L5 and L18 in the 5S rRNA

Three 5S rRNA-binding ribosomal proteins (L5, L18, TL5) of extremely thermo philic bacterium Thermus thermophilus have earlier been isolated. Structura l analysis of their complexes with rRNA requires identification of their bi nding sites in the 5S rRNA. Previously, a TL5-binding site has been identif ied, a TL5-RNA complex crystallized, and its structure determined to 2.3 An gstrom. The sites for L5 and L18 were characterized, and two corresponding 5S rRNA fragments constructed. Of these, a 34-nt fragment specifically inte racted 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.