Here, we demonstrated that recombinant protein, designated C176, derived from Scl1.41 of the GAS M41-type strain also binds both plasma

and purified high-density lipoprotein (HDL). Next, we determined that the intact click here noncollagenous region of C176 was necessary and sufficient for HDL binding. C176–HDL interaction could be eliminated by the presence of low concentrations of the nonionic detergent, Tween 20, indicating the hydrophobic nature of this interaction. We finally showed that whole GAS cells expressing native Scl1.41 protein absorbed HDL from human plasma in the absence of Tween 20, but M6-type GAS cells did not. Altogether, our results add further evidence to the importance of GAS–lipoprotein binding. As an important species of Gram-positive bacterial pathogens, Streptococcus pyogenes [group A Streptococcus (GAS)] is responsible for a number of suppurative infections including pharyngitis, impetigo/pyoderma, erysipelas, cellulitis, necrotizing fasciitis, toxic streptococcal syndrome, and scarlet fever, as well as nonsuppurative

sequelae including acute rheumatic fever, Selleck EGFR inhibitor and acute glomerulonephritis (Cunningham, 2000). Major virulence factors of GAS include lipoteichoic acid (LTA), the surface-exposed M protein, hyaluronic acid capsule, as well as several other cell surface proteins that include the streptococcal collagen-like surface protein 1 (Scl1) (Lukomski et al., 2000; Rasmussen et al., 2000). Based on the surface M protein, GAS is serologically separated into over 100 Urease M protein serotypes (Beall et al., 1996). Because two cell-surface streptococcal collagen-like proteins, Scl1 and Scl2 (also known as SclA and SclB), were identified in 2000 (Lukomski et al., 2000; Rasmussen et al., 2000), their structure and functions have been studied extensively (Lukomski et al., 2000, 2001;

Rasmussen et al., 2000; Rasmussen & Björck, 2001; Whatmore, 2001; Humtsoe et al., 2005; Han et al., 2006a, b; Påhlman et al., 2007; Caswell et al., 2008). Mature Scl1 proteins are demonstrated to contain the N-terminal noncollagenous variable (V) regions, the adjacent collagen-like (CL) regions, linker (L) regions, and cell-wall/membrane (WM) regions. Scl2 proteins are similar to Scl1 in structure, but they lack the linker regions (Lukomski et al., 2000). Both Scl1 and Scl2 share a common ‘lollipop-like’ structure with stalks made of the CL regions and globular heads made of the V regions. CL regions are of disparate lengths and vary in the Gly–Xaa–Yaa (GXY) repeat content (Han et al., 2006b). It has been reported that Scl1 proteins from some GAS serotypes can interact with apolipoprotein B-containing lipoproteins, mainly low-density lipoprotein (LDL) in human plasma (Han et al., 2006a).