Figure 3. Ribosome dimerization occurs via interaction of the C‐terminal domain of SaHPF, and via interactions involving h26.

1. View of the density maps for unrotated ribosome‐bound SaHPF, emphasizing the dimer interface (magenta, SaHPF; orange, h26; LSU omitted for clarity; orientations as in Fig 2). The density for CTD (interface) derives from the same but Gaussian‐filtered (2.0 SD) high‐resolution map.
2. Side chains of amino acids from the N‐terminal domain of SaHPF are visible in the density map (left; unfiltered map). Helix 26 stabilizes dimer formation in the “tight” dimer (center; unfiltered map).
3. SaHPF‐CTD forms a dimer in solution. ¹⁵N,¹H‐HSQC spectrum of the C‐terminal domain of SaHPF showing backbone amide resonances (left). The spectrum was recorded at a proton resonance frequency of 700 MHz at 35°C, in PBS buffer (90% H₂O + 10% D₂O) at pH 7.6 with 200 mM NH₄Cl concentration. Backbone superimposition of the 10 final simulated annealing structures in two orientations (right).
4. Dimerization of the C‐terminal domain of SaHPF from two ribosomes within a dimer (map filtered at 2.0 SD using a Gaussian filter). Residues involved in hydrophobic interactions at the interface of the two CTDs are shown as sticks. The region of potential interaction of CTD with bS2 is marked by *.