Role For Cell-Surface Collagen Of Streptococcus Pyogenes In Infections

Group A Streptococcus (GAS) displays cell-surface proteins that resemble human collagen. We find that a fluorophore-labeled collagen mimetic peptide (CMP) labels GAS cells but not Escherichia coli or Bacillus subtilis cells, which lack such proteins. The CMP likely engages in a heterotrimeric helix with endogenous collagen, as the nonnatural D enantiomer of the CMP does not label GAS cells. To identify a molecular target, we used reverse genetics to "knock-in" the GAS genes that encode two proteins with collagenlike domains, Scll and Sc12, into B. subtilis. The fluorescent CMP labels the cells of these B. subtilis strains. Moreover, these strains bind tightly to a surface of mammalian collagen. These data are consistent with streptococcal collagen forming triple helices with damaged collagen in a wound bed and thus have implications for microbial virulence.