Identification of small molecules affecting the interaction between human hemoglobin and Staphylococcus aureus IsdB...

Area of Science:

• Microbiology
• Biochemistry
• Drug Discovery

Background:

• Staphylococcus aureus utilizes human hemoglobin (Hb) as a primary iron source.
• The Iron-regulated surface determinant (Isd) system facilitates Hb binding, heme extraction, and iron acquisition by S. aureus.
• IsdB, a surface protein of the Isd system, is crucial for Hb binding and acts as a virulence factor.

Purpose of the Study:

• To identify small molecules capable of inhibiting the protein-protein interaction (PPI) between IsdB and Hb.
• To establish a pipeline for discovering and testing IsdB:Hb PPI inhibitors.

Main Methods:

• Structure-based virtual screening to identify potential inhibitor compounds.
• Ad hoc immunoassay for screening commercially available compounds.
• Saturation-transfer difference (STD) NMR to verify specific molecular interactions.
• Isothermal titration calorimetry (ITC) to quantify binding affinity.

Main Results:

• A virtual screening campaign identified candidate molecules disrupting IsdB:Hb interaction.
• An immunoassay confirmed the efficacy of selected compounds in reducing Hb bound to IsdB.
• STD NMR verified direct binding of molecules to IsdB.
• ITC analysis revealed a lead compound with low micromolar binding affinity to Hb.

Conclusions:

• The developed in silico/in vitro pipeline is effective for discovering and testing IsdB:Hb PPI inhibitors.
• The identified lead compound serves as a starting point for further optimization and development of new antimicrobials.