Structure/Function Analysis of a Novel Myeloperoxidase Inhibitor from Staphylococcus delphini

Abstract

Staphylococcus aureus and closely related species are highly adapted to their hosts and have evolved many strategies to resist opsonization and phagocytosis. S. aureus shows resistance to killing following uptake into the phagosome, which suggests that the bacterium can actively evade specific intracellular killing mechanisms used by neutrophils. We recently discovered a highly conserved S.aureus protein (SPIN for Staphylococcal Peroxidase INhibitor) that specifically binds and inhibits myeloperoxidase (MPO), a major player in the oxidative defense of neutrophils [de Jong et al., PNAS, 2017]. S. aureus cells deleted for SPIN gene showed decreased survival compared to wild‐type bacteria after phagocytosis by neutrophils. A crystal structure of SPIN bound to MPO suggests that it acts as a molecular plug that prevents H2O2 substrate access to the MPO active site. To further our understanding of the structure/function relationships of SPIN proteins, we cloned, overexpressed, purified, and characterized a series of SPIN orthologs of Staphylococcal origin.We found that SPIN originating from S. delphini although shares only ~53% identity to SPIN‐aureus, it still retained a strong affinity and inhibitory capacity for human MPO. A 2.4 Å crystal structure of SPIN‐delphini bound to human MPO provided a basis for comparing the similarities and differences between SPIN‐aureus and SPIN‐delphini. Together, these studies shed light on the molecular features which determine the specificity of SPIN proteins for MPO, and suggest potential avenues for using this information toward the design of synthetic MPO inhibitors.Support or Funding InformationNIH Grants AI111203 and GM121511This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.