Here we demonstrated that truncated Scl1 fused with OmpA was directed to the outer membrane fraction of E. coli by western blot analysis, and likely exposed on the surface of E.
coli by FACS analysis. While ectopic expression of Scl1 on the heterologous bacteria E. coli is an alternative approach to reduce the potential interference of other factors on the surface of S. pyogenes, there are some limitations in our study. For example, it can not be ruled out that Scl1 protein was secreted to the periplasmic space, because Scl1 was Tozasertib in vivo constructed after the OmpA signal sequence. To avoid this problem, we performed FACS analysis on whole bacteria using Scl1 antibodies to detect the location of Scl1 in/on E. coli. FACS CYC202 cell line analysis has been widely used in identification of cell surface molecules in many immunologic and hematologic studies. Furthermore, we isolated proteins from the outer membrane fraction and confirmed the existence of Scl1 by western blot analysis with antibodies check details against Scl1 and its fusion protein OmpA. However, the proper folding of ectopically expressed Scl1 and the integrity of the outer membrane of E. coli account for other issues influencing our interpretation of Scl1 in adhesion. Nevertheless, our findings concerning the adherence of Scl1-expressed E. coli to human epithelial cells unequivocally show that Scl1 contributes significantly to the adhesion of bacteria to human
epithelial cells. Collagen is a triple-helical, elongated protein structure Pomalidomide concentration that is the main structural component
of the extra-cellular matrix in all multicellular organisms. Collagen-like sequences are found not only in proteins of multicellular organisms but also in proteins of microorganisms, such as a pullulanase in Klebsiella pneuminiae [28] and a platelet aggregation-associated protein in S. sanguis [29, 30]. Moreover, collagens interact with several macromolecules in a specific manner, suggesting that the collagen-like repeat sequences not only play a basic structural role, but also have a functional significance. Many eukaryotic cells bind collagen through integrins expressed on their surface [11]. Studies have demonstrated that the recombinant Scl1.41 protein interacted with α2β1 and α11β1 integrins, induced intracellular signaling in host cells, and promoted the internalization of S. pyogenes [9, 12, 13]. While the hypothesized region mediating the binding to α2β1 and α11β1 integrins in the recombinant Scl1.41 is in a motif called the GLPGER motif [9, 12, 13], Scl1 protein of S. pyogenes M29588 strain in our study does not contain the GLPGER motif. The novel aspect of this study is the observation that, in this Scl1 sequence type, the GLPGER motif is absent, yet adherence is maintained. Nevertheless, our results indicate that protein receptors, α2 and β1 integrins, contribute to Scl1-dependent binding to the surface of human epithelial cells.