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. Author manuscript; available in PMC: 2013 Apr 26.
Published in final edited form as: Cell. 2012 Oct 26;151(3):497–507. doi: 10.1016/j.cell.2012.09.033

Figure 6. Structural convergence between group II introns and protein endonucleases.

Figure 6

Stereo representation of the intron active site (K+/Ca2+ oligonucleotide-bound structure, blue) superimposed over the R active site of endonuclease BamHI (PDB id.: 2BAM, red). The carboxyl groups of amino acids Glu77 and Asp94 occupy the same location as the phosphates of nucleotides U375 and C377 (D5 bulge), the carbonyl oxygen of Phe112 and other solvent molecules (WA and WB) replace the phosphates of C358-G359 (D5 catalytic triad), Lys126 is analogous to the K2 ion, and Tyr65 plays the same role as the K1 ion. As a consequence, the catalytic ions M1 and M2 and also the reaction nucleophile superimpose precisely.