Fig. 6: Analysis of BT4244, ZmpB, IMPa, ZmpC, OgpA, and AM0627 active sites.

a Close-up view of the active sites of BT4244-Tn O-glycan, ZmpB,-mSTb, IMPa-T O-glycans, ZmpC-mSTb, and OgpA-T-glycopeptide complexes. Note that the zinc ion is not present in the structure of OgpA in complex with the T-glycopeptide because an inactive version of OgpA was used in which the His205, a residue that coordinates the Zn²⁺, and the catalytic Glu206 was mutated to Ala²⁰. The ligands and the Zn²⁺ in these structures are shown as olive carbon atoms and as a pink sphere, respectively. The amino acids of the enzymes are shown as cyan carbon atoms. The dotted lines are displayed as brown and yellow for the hydrogen bonds and the interactions between the metal and the amino acids, respectively. b Active sites of BT4244-Tn O-glycan, ZmpB,-mSTb O-glycan, IMPa-T O-glycan, ZmpC-mSTb O-glycan, and OgpA-T-glycopeptide complexes showing the superimposed P1 from AM0627^E326A–P1–Zn²⁺ complex. P1 is colored as in Figs. 2 and 3. The red arrow indicates the presence of the conserved Tyr723^BT4244 with Tyr470^AM0627, and the red circle indicates that the Tyr is not present in ZmpB/ZmpC and that a steric clash might occur between Thr775/Tyr776^IMPa and the sugar units at G1 and G2.