AMA binds Ni2+ with picomolar affinity, as discovered through a structural analysis. The affinity of AMA for Ni2+ was found to be 80 pM, competing with Zn2+ for binding. Further studies revealed that AMA and its metal complexes interact with the Ni-dependent enzymes in bacteria, affecting their activity. Interestingly, Zn-AMA and Co-AMA significantly suppressed enzyme activity, more so than a clinically approved inhibitor. However, in S. aureus, AMA and its metal complexes had a different effect, inhibiting enzyme activity similarly.
In exploring the mechanism of action of Zn-AMA, it was found that it binds to the periplasmic protein NikA, inhibiting Ni2+ uptake. The crystal structure of NikA in complex with Ni-AMA provided insight into the binding interactions. Additionally, structure-activity relationship studies revealed that analogs of AMA with specific substitutions showed varied affinities for NikA, influencing their biological activity. In vivo toxicity studies demonstrated that Zn-AMA was not toxic to cells. Moreover, in vivo efficacy studies using G. mellonella larvae showed that Zn-AMA was effective in reducing the virulence of K. pneumoniae and S. aureus when used as a single treatment.
Overall, the findings suggest that AMA and its metal complexes, particularly Zn-AMA, are promising candidates for inhibiting Ni-dependent enzymes and reducing the virulence of bacterial infections. Further research into the mechanism of action and structure-activity relationships of these compounds could lead to the development of new antimicrobial agents.
