Crystal structures of fibronectin-binding sites from Staphylococcus aureus FnBPA in complex with fibronectin domains

Abstract

Staphylococcus aureus can adhere to and invade endothelial cells by binding to the human protein fibronectin (Fn). FnBPA and FnBPB, cell wall-attached proteins from S. aureus, have multiple, intrinsically disordered, high-affinity binding repeats (FnBRs) for Fn. Here, 30 years after the first report of S. aureus/Fn interactions, we present four crystal structures that together comprise the structures of two complete FnBRs, each in complex with four of the N-terminal modules of Fn. Each Ϸ40-residue FnBR forms antiparallel strands along the triple-stranded ␤-sheets of four sequential F1 modules ( 2-5 F1) with each FnBR/ 2-5 F1 interface burying a total surface area of Ϸ4,300 Å 2 . The structures reveal the roles of residues conserved between S. aureus and Streptococcus pyogenes FnBRs and show that there are few linker residues between FnBRs. The ability to form large intermolecular interfaces with relatively few residues has been proposed to be a feature of disordered proteins, and S. aureus/Fn interactions provide an unusual illustration of this efficiency.intrinsic disorder ͉ tandem ␤-zipper ͉ host-pathogen interaction S taphylococcus aureus is a dangerous human pathogen that causes a wide range of debilitating and life-threatening infections (1). Incidence of S. aureus resistance to antibiotics (2) makes the understanding of its mechanisms of pathogenesis imperative. S. aureus/Fn interactions were first reported 30 years ago, and an S. aureus Fn-binding protein was isolated and characterized Ϸ20 years ago (3). Our recent work has dissected the 363-residue C-terminal region of FnBPA into 11 FnBRs (4) (FnBPA1-11; Fig. 1 A and B), six of which bind the NTD (N-terminal domain) of Fn (comprising modules 1-5 F1) with dissociation constants in the nanomolar range (5). The Cterminal region of FnBPB, a second S. aureus Fn-binding protein, is very similar to FnBPA but lacks one of the shorter FnBRs (5). In FnBPA, which also binds fibrinogen, the fibrinogen-and Fn-binding regions (Fig. 1 A) appear to cooperate in disease progression, with the FnBR region being particularly associated with persistence of infection (6). FnBPA/Fn interactions both mediate S. aureus invasion of (7) and activate endothelial cells, evoking both the proinflammatory and procoagulant responses typical of infective endocarditis (8). FnBPAs ability to mediate platelet activation, a key step in thrombus formation, is also likely to play a role in cardiovascular disease (9) and FnBPA has been implicated in cardiac device infections through its ability to mediate S. aureus attachment to implanted prosthetic materials (10). We previously predicted that in Fn-BPA each FnBR binds a string of three or four F1 modules in the NTD of Fn through a longer version of the tandem ␤-zipper mechanism that we discovered in Streptococcus dysgalactiae interactions with 1 F1 2 F1 (4). Results and DiscussionCrystal Structure of FnBPA-1/ 2-5 F1. Fig. 1C shows two F1 module pair/peptide structures that together comprise the structure of the most N-terminal S. aureus FnBR (...

Identification and structural analysis of type I collagen sites in complex with fibronectin fragments

“…This type of binding is similar to that of proteins from pathogenic bacteria in complex with FnI modules (Fig. 3B) (21,22), which indicates a functional similarity between the collagen and bacterial protein interactions with FN. It is worth noting that the isolated peptide in solution does not adopt a stable ␤-strand conformation (Fig.…”

“…Datasets, to a maximum resolution of 2.1 Å, were collected at the Diamond Light Source synchrotron facility (Didcot, U.K.); dataset and refinement statistics are shown in Table S2. Both 8 FnI and 9 FnI exhibit canonical FnI (21,22) structures (Fig. 3A), with a double-and a triple-stranded antiparallel ␤-sheet (strands A,B and C,D,E, respectively) stabilized by disulfide bonds between strands A/D and D/E.…”

Fibronectin Binds to and Induces Conformational Change in a Disordered Region of Leptospiral Immunoglobulin-like Protein B

“…Similarly, upon binding to NTD, LigBCen2NR folds into a ␤-strand-rich structure, much like the D123 domain of FnbPA or the N-terminal of BBK32 (21). High resolution structures of the complex between the B3 region of FnbB and the first and the second type I module of Fn (17,18) and the complex between the first or the fifth Fn binding region of FnbpA and the second to the fifth type I module of Fn (23,39,46) all indicate that a two ␤-strand complex, called a ␤-zipper, mediates those interactions. The binding of Sfb and BBK32 to NTD are also accomplished through the ␤-zipper interaction (23, 39, 46).…”

“…Disordered proteins often alter their conformations when binding their partners (50). One possible role of protein disorder in protein-protein interactions is the large accessible surface area per residue contributed by the disordered protein (18,51). The unfavorable decrease in the entropy of LigBCen2NR upon binding NTD due to the disorder-order transition is offset by a larger increase in entropy, possibly due to hydrophobic interactions, as demonstrated by ITC.…”

“…Known interaction modes between Fn and bacterial Fn-binding proteins include the ␤-zipper (17,18) and the cationic cradle (19). It was recently discovered that the Fn-binding domains in certain Fnbinding proteins are disordered and extended but gain structure upon binding to the NTD of Fn (20 -22).…”