Antibodies against Slr are developed during a S. pyogenes infection in humans and an S. pyogenes strain lacking Slr had lower resistance against neutrophil phagocytosis in vitro and was less virulent in a mouse model of infection. Slr lacks a LPXTG motif, which links Gram-positive proteins to the cell wall; instead a TLIA lipobox is present and acts as a membrane anchoring motif. The Slr protein is similar to virulence proteins of the internalin family of L. monocytogenes but there are differences between the proteins. The LRR region in Slr is located in the Cterminal half of the molecule unlike the members of the internalin family in which the LRR region is located in the N-terminal part of the protein. At the end of the N-terminal region there are four histidine triad motifs that are not present in the internalin family of proteins. Adherence of human pathogens to certain tissue components might reflect preferences for specific sites of infection. Bacterial adhesins that interact with extracellular matrix components such as collagen, fibronectin, fibrinogen and laminin-related polysaccharides have been identified for both Gram-negative and Grampositive bacteria. Groups A, B, C, D and G streptococci have all been shown to exhibit collagen binding ability. Protein FOG is one of the proteins that recruit collagen type I in group G streptococci. For S. pyogenes, adhesion to collagen type IV by surface protein M3 has been reported as well as binding to Mnegative strains. Since Slr is a putative surface located lipoprotein containing LRR motifs, we hypothesized that Slr could mediate binding to collagen. In this study we present experimental evidence that Slr is a surface attached lipoprotein containing LRR regions. Furthermore, using electron microscopy of immunogold labeled Slr and other experimental techniques, we were able to show that Slr is a collagen I binding protein. One of the most studied virulence factors of S. pyogenes is the cell wall anchoredM protein. It is involved in adherence to human epithelial cells, such as buccal cells and epidermal keratinocytes. The M protein is also intimately linked to antiphagocytic properties and intracellular survival in phagocytic cells. Of particular interest for the present study is that the M6 protein present on the surface of S. pyogenes of M6 serotype has been suggested to camouflage the LRR lipoprotein Slr from Slr antibody recognition. Lipoproteins from Gram-positive SCH772984 customer reviews bacteria are not as well studied as cell wall anchored proteins, but several recent studies have suggested that lipoproteins also are important for immune GDC-0941 evasion and adherence during colonization and infection. Furthermore, several lipoproteins have shown promise as vaccine candidates. Previously described lipoproteins of S. pyogenes are linked to metal transport as acquisition, most of them belong to ABC transport systems and some have been shown to be virulence factors in animal models of infection.