Poster Presentation The 44th Lorne Conference on Protein Structure and Function 2019

Identification of small molecules exhibiting oxacillin synergy through direct inhibition of VraS and inhibition of vraSTR expression in methicillin resistant Staphylococcus aureus (#160)

Michael E Johnson 1 , Hyun Lee 1 , Susan Boyle-Vavra 2 , Jinhong Ren 1 , Shaohui Yin 2 , Robert S Daum 2
  1. Center for Biomolecular Sciences, University of Illinois at Chicago, Chicago, IL, United States
  2. Department of Pediatrics, University of Chicago, Chicago, Illinois, United States

Methicillin-resistant Staphylococcus aureus (MRSA) strains that are resistant to all forms of penicillin have become an increasingly common problem threatening human health.  They are responsible for a wide variety of infectious diseases ranging from minor skin abscesses to life-threatening severe infections.  The vra operon that is conserved among S. aureus strains encodes a three-component signal transduction system (vraSTR) that is responsible for sensing and responding to cell-wall stress. We developed a novel and multi-faceted assay to identify compounds that potentiate the activity of oxacillin, essentially restoring efficacy of oxacillin against MRSA, and performed high-throughput screening (HTS) to identify oxacillin potentiators.  HTS of 13,840 small molecule compounds from an antimicrobial-focused Life Chemicals library, using the MRSA cell-based assay, identified three different inhibitor scaffolds.  Checkerboard assays for synergy with oxacillin, RT-PCR assays against vraR expression and direct confirmation of interaction with VraS by surface plasmon resonance (SPR) further verified them to be viable hit compounds.  Subsequent SAR study of the best scaffold with diverse analogs was utilized to improve potency, and provides a strong foundation for further development. Co-crystallization is in progress.