Molecular modeling of ceftriaxone activation in the active sites of penicillin-binding proteins 2

The enzyme—substrate complexes of penicillin-binding proteins PBP2 from FA19, 35/02, and H041 strains of Nisseria gonorrhoeae with ceftriaxone were simulated by the molecular dynamics method with the combined quantum mechanics/molecular mechanics potentials. The hydrogen bond lengths between the carbonyl oxygen atom of the substrate and amino acid residues of the oxyanion hole, as well as the distances of the nucleophilic attack by the oxygen atom of the catalytic serine of the carbonyl carbon atom of the substrate were considered. The 2D maps of the Laplacian of electron density show a more efficient activation of the substrate by the wild type enzyme rather than mutated species. This is consistent with the geometry features: distributions of the lengths of hydrogen bonds forming oxyanion hole and nucleophilic attack distance that are shifted toward lower values.