Figure 8. RF3 nucleotide loading-and-release.
(A) RF3•GTP with the nucleotide-binding pocket inside the red box. (B)–(D) Nucleotide-binding pockets of RF3•GDP, apo-RF3 and RF3•GTP. In RF3•GDP, GDP is stabilized by interaction with H92. In apo-RF3 (B) and in RF3•GTP (C) H92 is retracted away from the nucleotide-binding pocket. Instead, this stabilization is performed by a Mg2+ ion. (E) Superimposition of H92 position (black box in [B]–[D]) showing H92 in its GDP-stabilizing position (blue) and in its retracted positions (green and gray).