FIGURE 4.

Thermodynamic linkage between S4 and other 5′-domain proteins. The linking free energy, ΔG_link, for the native complex (striped bars), flipped complex (gray bars), and α (black bars) was calculated as ΔG_link^○=ΔG_S4+j^○−ΔG_S4^○ in which j indicates a combination of ribosomal proteins S16, S17, and S20. Free energies for S4 binding, ΔG_S4^○=RT ln K_dS4, were evaluated at 37°C (Supplemental Table S3). ΔΔG_α^○=ΔΔG_F^○−ΔΔG_N^○ represents how other 5′-domain proteins alter the linkage between S4 binding and Mg²⁺-dependent folding of 16S helix 3.