Crystal Structure of an Invasivity-Associated Domain of SdrE in <i>S</i>. <i>aureus</i>

<div><p>The surface protein SdrE, a microbial surface components recognizing adhesive matrix molecule (MSCRAMM) family protein expressed on the surface of <i>Staphylococcus aureus</i> (<i>S</i>. <i>aureus</i>), can recognize human complement regulator Factor H and C4BP, thus making it a potentially promising vaccine candidate. In this study, SdrE^278-591 was found to directly affect <i>S</i>. <i>aureus</i> host cell invasion. Additionally, the crystal structure of SdrE^278-591 at a resolution of 1.25 Å was established, with the three-dimensional structure revealing N2-N3 domains which fold in a manner similar to an IgG fold. Furthermore, a putative ligand binding site located at a conserved charged groove formed by the interface between N2 and N3 domains was identified, with β2 suspected to occupy the ligand recognizing site and undergo a structural rearrangement to allow ligand binding. Overall, these findings have further contributed to the understanding of SdrE as a key factor for <i>S</i>. <i>aureus</i> invasivity and will enable a better understanding of bacterial infection processes.</p></div

Adherence and invasion of the ΔSdrE and ΔSdrE^278-591 mutants in host cell lines <i>in vitro</i>.

<p><i>S</i>. <i>aureus</i> Mu50 and its isogenic mutants <i>ΔSdrE</i> (Mu50Δ<i>SdrE</i>) and ΔSdrE^278-591 (Mu50Δ<i>SdrE-A</i>) were examined for adherence in HeLa (A) and 143B cells (B). These same mutants were also examined for invasivity in HeLa (C) and 143B (D) cells. Infectivity assessments were conducted for 4 h at 37°C. Wild-type <i>S</i>. <i>aureus</i> and the <i>ΔSdrE</i> (Mu50<i>ΔSdrE</i>) and <i>ΔSdrE</i>^278-591(Mu50<i>ΔSdrE-A</i>) mutants were generated to be devoid of SdrE in order to avoid destruction of the monolayer infection system. Scoring of the number of adherent and invasive bacterial cells indicate that adhesion and invasion are substantially reduced for <i>ΔSdrE</i> ((Mu50<i>ΔSdrE</i>) and <i>ΔSdrE</i>^278-591 -deficient (Mu50<i>ΔSdrE-A</i>) <i>S</i>. <i>aureus</i> mutant. Results are presented as a mean ± standard deviation for at least three independent experiments. Asterisks and triangles denote values significantly different from the wild-type as determined by Student’s t-test (** P < 0.01).</p

<i>S</i>. <i>aureus</i> SdrE^278-591 (magenta) superimposed on its homolog <i>S</i>. <i>aureus</i> Bbp (cyan).

<p>(A) <i>S</i>. <i>aureus</i> SdrE^278-591 (magenta) superimposed on its homolog Bbp (substrate free, PDB code 5cf3). (B) <i>S</i>. <i>aureus</i> SdrE^278-591 (magenta) superimposed on its homolog Bbp (substrate, PDB code 5cfa). The predominantly green strand is the peptide ligand (substrate).</p

Data collection and refinement statistics.

<p>Data collection and refinement statistics.</p