Abstract
The extracellular adherence protein (Eap) of Staphylococcus aureus is a secreted protein known to exert a number of adhesive and immunomodulatory properties. Here we describe the intrinsic DNA binding activity of this multifunctional secretory factor. By using atomic force microscopy, we provide evidence that Eap can bind and aggregate DNA. While the origin of the DNA substrate (e.g., eukaryotic, bacterial, phage, and artificial DNA) seems to not be of major importance, the DNA structure (e.g., linear or circular) plays a critical role with respect to the ability of Eap to bind and condense DNA. Further functional assays corroborated the nature of Eap as a DNA binding protein, since Eap suppressed the formation of “neutrophil extracellular traps” (NETs), composed of DNA-histone scaffolds, which are thought to function as a neutrophil-mediated extracellular trapping mechanism. The DNA binding and aggregation activity of Eap may thereby protect S. aureus against a specific anti-microbial defense reaction from the host.
Highlights
Staphylococcus aureus is an opportunistic pathogen and a major cause of acute, as well as, chronic skin and soft tissue infections (SSTIs) (Moet et al, 2007)
Biofilm formation by S. aureus is a complex process that commonly includes the formation of an extracellular polymeric matrix including polysaccharide intercellular adhesin (PIA), protein to protein interactions, and the incorporation of extracellular DNA; which are all used by multiplying S. aureus cells to form and to remain within the multilayered structure (O’Gara, 2007; Payne and Boles, 2016). β-hemolysin has been identified as a factor that can bind to eDNA (Huseby et al, 2010), this exotoxin is not produced by most clinical S. aureus isolates due to the insertion of a prophage into the β-hemolysin encoding hlb gene (Goerke et al, 2009)
The secreted adhesive protein extracellular adherence protein (Eap) of S. aureus is a multifunctional protein that exerts a number of immunomodulatory functions (Chavakis et al, 2005), with regard to protection of bacteria against host defense machineries
Summary
Staphylococcus aureus is an opportunistic pathogen and a major cause of acute, as well as, chronic skin and soft tissue infections (SSTIs) (Moet et al, 2007). Β-hemolysin has been identified as a factor that can bind to eDNA (Huseby et al, 2010), this exotoxin is not produced by most clinical S. aureus isolates due to the insertion of a prophage into the β-hemolysin encoding hlb gene (Goerke et al, 2009) Another S. aureus factor which may serve as binding partner for eDNA on the bacterial surface is extracellular adherence protein (Eap), a member of the “secretable expanded repertoire adhesive molecules” (SERAM) protein family (Chavakis et al, 2005). Depending on the S. aureus strain background, this cationic protein consists of four to six similar, but not identical, repeats of about 100 amino acid residues each; these are designated EAP modules, which are connected by short 9–12 residues long linker regions (Hammel et al, 2007)
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