RESUMO
Currently prescribed antibiotics target the catalytic sites of wild-type bacterial proteins; however, bacteria adopt mutations at this site, eventually leading to the emergence of resistance. Therefore, the identification of alternative drug binding sites is crucial, which requires knowledge of the dynamics of the mutant protein. Here, we set out to investigate the impact of a high-resistance-causing triple mutation (S385T + L389F + N526K) on the dynamics of a prioritized resistant pathogen, Haemophilus influenzae, using computational techniques. We studied penicillin-binding protein 3 (PBP3) and its complex with FtsW, which display resistance toward ß-lactam antibiotics. We showed that mutations displayed local and nonlocal effects. In terms of the former, the orientation of the ß-sheet, which surrounds the active site of PBP3, was impacted and the catalytic site was exposed to the periplasmic region. In addition, the flexibility of the ß3-ß4 loop, which modulates the catalysis of the enzyme, increased in the mutant FtsW-PBP3 complex. As for nonlocal effects, the dynamics of the pedestal domain (N-terminal periplasmic modulus (N-t)), i.e., the opening of the fork, was different between the wild-type and mutant enzymes. We showed the closed fork caused a greater number of residues to participate in the hypothesized allosteric communication network connecting N-t to the transpeptidase domain in the mutant enzyme. Finally, we demonstrated that the closed fork results in more favorable binding with ß-lactam antibiotics, particularly cefixime, suggesting that small therapeutics that can stabilize the closed fork of mutant PBP3 may lead to the development of more effective molecules to combat resistant bacteria.
