Function Of Csm3 Protein From Mycobacterium Tuberculosis

Mycobacterium tuberculosis(Mtb),the causative agent of tuberculosis(TB).According to the WHO,2015 Global TB report shows that a third of people worldwide carry Mtb,which can be long-term potential in the host,requires constant drug treatment,leading to the growing number of multi-drug-resistant strains and pan-resistant strains,which bring a huge threat and challenge for TB control.Therefore,it is crucial to strengthen the basic research of Mtb,especially the research of its pathogenicity,which is the key to develop anti-TB drugs and the diagnosis and treatment of TB.CRISPR-Cas systems are prokaryotic adaptive immune systems that defend against invading nucleic acids.The CRISPR-Cas system of Mtb belong to ?-A subtype,it is mainly used for typing,but its biological function has not been reported.Here,we investigated the Csm3 protein of CRISPR-Cas system.we prepared the polyclonal antibody against Csm3 and found that the Csm3 was a secreted protein,which can help the bacteria to resist the phagocytosis of macrophages,enhancing the bacterial virulence.In addition,we also found that Csm3 could not induce the apoptosis of HTP-1 macrophages but could cause a weaker T cell response.These results indicated that the CRISPR-Cas system of Mtb could not only help the bacteria to resist foreign invasion,but also related to the bacterial virulence and host immunity.At the same time,we purified Cas proteins and HtpG in vitro,by Co-IP and GST pull-down assays identified the interaction between Csm3 and other Cas proteins,analyzed the relationship between protein components.We further studied the relations between Csm3 and crRNA,so that we have more in-depth understanding of the CRISPR-Cas system.In addition,we purified crRNA-Csm complex.However,because of its purity is not enough,so we need further purification.