Binding of the S7 protein with fragment 926-986/1219-1393 of the 16S rRNA as a key step in the assembly of the small subunit of prokaryotic ribosomes

Both structural and thermodynamic studies are necessary to understand the r ibosome assembly. An initial step was made in studying the interaction betw een a 16S rRNA fragment and S7, a key protein in assembling the prokaryotic ribosome small subunit. The apparent dissociation constant was obtained fo r complexes of recombinant Escherichia coli and Thermus thermophilus S7 wit h a fragment of the 3 ' domain of the E. coli 16S rRNA. Both proteins showe d high rRNA-binding activity, which was not observed earlier. Since RNA and proteins are conformationally labile, their folding must be considered to correctly describe the RNA-protein interactions.