Figure 1
From: Translational roles of the C75 2′OH in an in vitro tRNA transcript at the ribosomal A, P and E sites
Interactions of the tRNA C75 2′OH in ribosomal A-, P- and E-sites in crystal structures. (a) tRNA substrates at the aminoacyl (green), peptidyl (yellow) and exit (red) sites on the 70S ribosome in 3 dimensions. The PTC is circled. (b) Two-dimensional chemical structures showing the covalent bonds separating the C75 2′OH groups (circled) from the nucleophile and electrophile of the peptidyl transfer reaction (blue arrow). (c–e) Crystal structures of the A-, P- and E-site tRNA substrates, respectively. Models were constructed with UCSF Chimera and PDB file 1VY418. In the original PDB file, three water molecules found within the PTC were proposed to be essential for forming a “proton wire” to couple AA-tRNA accommodation and peptide bond formation. Two of these water molecules are ringed with white dashed circles and labeled W1 and W2 (W3 is not visible in this view). H-bonds are shown with white thin lines. (c) A-site Phe-tRNAPhe in green, with the 2′OH in magenta. C75 forms a Watson-Crick base pair with G2553 of 23S rRNA, and the 2′OH of C75 forms an H bond with the O4 of the A76 sugar pucker. N indicates that Phe was linked to the tRNA with an amide bond. (d) P-site fMet-tRNAfMet in yellow, with the 2′OH in magenta. C75 forms a Watson-Crick base pair with G2251 of 23S rRNA, and the 2′OH of C75 forms H bonds with W2 and the 2′OH of ribose C2073 of 23S rRNA. N indicates that fMet was linked to the tRNA with an amide bond. (e) E-site tRNAPhe in red, with the 2′OH in magenta. C75 does not form a base pair, whereas the 2′OH of C75 forms an H-bond with the N7 of the base of A76 in the same tRNA.
