Fig. 4
Structural analysis of MT13-C. a Crystal structure of the core MTase domain of MT13-C in complex with AdoHcy. The 7BS fold is shown in ribbon representation in green with AdoHcy shown in stick model in salmon. Unresolved density for the backbone of Lys578 is indicated by a dashed line. b Key AdoHcy binding residues in MT13-C and comparison with SpdS (PDB code 2o06). AdoHcy and the residues involved in its coordination in the MT13-C structure are shown in stick representation in green, whereas corresponding residues and the MTA cofactor in the SpdS structure are shown in gray. Sequence alignments illustrate the localization of these residues in key motifs. c Comparison of motif Post II residues between MT13-C and SpdS (PDB code 2o06). In the structural representation, motif Post II residues in MT13-C and SpdS are indicated as stick models in green and gray, respectively. The putrescine substrate of SpdS is indicated in magenta. The sequence alignment indicates the location of the corresponding residues in the respective primary sequences, and illustrates the conservation of motif Post II between METTL13 orthologs. d Surface representation of MT13-C showing sequence conservation. Evolutionary conservation was assessed using ConSurf web server47. The cofactor AdoHcy and docked eEFA1 hexapeptide (GKEKTH) are shown as stick models in green and yellow, respectively. e Close-up view of the MT13-C substrate binding site with docked peptide. AdoHcy and MT13-C residues predicted to interact with the N-terminal glycine (G2) are shown as stick model in green. The backbone of the substrate peptide (GKEKTH) is shown as stick model in yellow. f Mutational analysis of key residues in MT13-C. MT13-C protein constructs harboring indicated single amino acid substitutions were evaluated for MTase activity on eEF1A. Activities of mutant enzymes are represented as relative to wild type. Error bars represent s.d., n = 6
