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Inhibition of Myeloperoxidase by Staphylococcal SPIN Proteins
Author(s) -
Ploscariu Nicoleta T.,
Jong Nienke W.M.,
Ramyar Kasra X.,
Garcia Brandon L.,
Herrera Alvaro I.,
Prakash Om,
Haas PieterJan,
Strijp Jos A.G.,
Geisbrecht Brian V.
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.921.8
Subject(s) - myeloperoxidase , innate immune system , proteases , serine , staphylococcus aureus , immune system , virulence , microbiology and biotechnology , heme , chemistry , biology , peroxidase , inflammation , biochemistry , enzyme , bacteria , immunology , genetics , gene
Neutrophils are the most abundant type of white blood cells in humans and the most prominent cellular component of the innate immune system. They can be rapidly activated by various biochemical stimuli during the earliest phase of bacterial invasion and recruited into the sites of infection. Neutrophils contain subcellular granules that are replete with vital anti‐bacterial enzymes, including a series of chymotrypsin‐like Neutrophil Serine Proteases (NSPs) as well as a heme‐containing Myeloperoxidase (MPO). Work from the last decade has demonstrated that the pathogenic bacterium Staphylococcus aureus produces an array of virulence proteins that disrupt normal function of the human innate immune system. The combined activities of these proteins are believed to prolong bacterial survival within the host, allowing for infections to take hold. Given the critical role of neutrophils in responding to the initial stages of staphylococcal infection, we predicted that S. aureus might also express proteins that inhibit function of neutrophil granule components. Indeed, we recently identified two novel classes of S. aureus secreted proteins, EAP domain proteins and SPIN, which act as inhibitors of NSPs and MPO, respectively. SPIN (Staphylococcal Peroxidase INhibitor) is a previously uncharacterized protein found only in Staphylococci. SPIN potently inhibits MPO activity in a number of functional assays by forming a nanomolar affinity complex with MPO. To gain insight into the structure/function relationships of SPIN, we determined its structure bound to MPO by X‐ray crystallography. The structure of this complex implicates the N‐terminal ~10 amino acids as essential for SPIN function. To identify and further characterize key residues for SPIN function in more detail, we examined three types of SPIN proteins using structural methods, direct binding assays, and functional assays for MPO activity: (i) deletion mutants, (ii) SPIN proteins originating from divergent staphylococcal species, and (iii) a synthetically‐designed SPIN protein. The differences in binding and inhibition of MPO by these proteins not only provide a route for identifying the structure/function relationships in SPIN, they also constitute a template for the design of high‐affinity, synthetic MPO inhibitors based upon the properties of this unique immune evasion protein. Support or Funding Information AI11120302