Binding Of The Low-density Lipoprotein To Streptococcal Collagen-like Protein 1 Of Group A Streptococcus CMCC32198

Group A streptococcus (GAS) is one of the most pathogenic streptococcus, about 90% of streptococcal diseases are caused by GAS. The streptococcal collagen-like proteins, Scl1 and Scl2 (also known as SclA and SclB), have been identified since 2000 as a virulence protein factor of group A Streptococcus. Their structures are similar to collagen. Scl proteins can mediate adhesion to human lung epithelial cells and interact with other molecules, such as the human complement regulatory protein factor H, low-density lipoprotein, etc. The study explored whether Scl1 of GAS CMCC32198 bind to human low-density lipoprotein (LDL). The GAS was bought from Chinese Academy of Medical Sciences(CAMS). It will provide the basis for treatment of disease caused by GAS.In this study, primers of Scl1(C176) and its variable region (C176-v) of CMCC32198 were designed with the Primer D'Signer software (IBA, Gottingen, Germany). The gene were amplified through PCR. The recombinant vectors were constructed by incising of PCR products and ligating with pASK-IBA2 vector and then they were transformed into E.coli BL21. Positive bacteria was cultured and sequenced, the results showed the nucleotide sequences of C176 and C176-v are homology of 100% to the EF042101.1 listed in GenBank. Positive transformants were induced by anhydrotetracycline to express proteins. C176 and C176-v priteins were purified by the Strep-tactin purification system. Affinity chromatography were used to identify their ligands presented in human plasma. The results implied that C176 and C176-v proteins from GAS CMCC32198 could bind to the same ligand identified as low-density lipoprotein (LDL). The interactions between recombinant proteins C176, C176-v, GAS CMCC32198 and LDL were tested by Enzyme-linked immunosorbent assay (ELISA), the results showed that Scl1(C176) of GAS CMCC32198, its V region(C176-v) and GAS CMCC32198 could bind to LDL, and were concentration-dependent. The study has significant to understand the pathogenesis and treatment desease caused by GAS.