Figure 4
From: Structural insights into the RNA methyltransferase domain of METTL16
Proposed mechanism of methyl transfer catalyzed by METTL16. (A) A schematic of the chemical SN2 reaction of methyl transfer from SAM to N6-adenosine is shown with curved arrows to indicate movement of electron pairs. (B) To model methyl transfer, SAM (gray ball-and-stick representation) was modeled into the SAH-binding site of METTL16_40–291 (blue) and the methyl-acceptor adenosine (gray ball-and-stick representation) was modeled via superposition of an m6A DNA MTase, EcoP15l (PDB ID: 4zcf, chain B39), from E. coli bound to unmethylated DNA. Residues in the 184NPPF187 motif that are critical for catalysis are labeled. (C) Comparison of the apo METTL16_291 (green sticks), SAH-bound METTL16_291 (yellow sticks) and SAH-bound METTL16_40–291 (PDB ID: 2h0027, blue sticks) structures revealed different backbone conformations of the 184NPPFF188 motif; residue F188 could not be modeled in the METTL16_291/SAH structure. Side chains of P185 and P186 of METTL16_291/SAH are shown while the others have been removed for clarity. An arrow points to the cis-conformation between P185 and P186.
