Characteristics of Mycobacterium tuberculosis serine protease Rv1043c in enzymology and pathogenicity in mice

The serine proteases of Mycobacteria tuberculosis (Mtb) are important contributors to the process of bacterial invasion and its pathogenesis. In the present study, we systematically characterized the role of the Rv1043c protein in mycobacterium infection by purifying the Rv1043c protein in Escherichia coli and constructing a Mycobacterium smegmatis (Msg) strain overexpressing Rv1043c (Msg_Rv1043c). We found that Rv1043c had serine protease activity and localized to the surface of Mtb. We determined that the optimal pH and temperature for the Rv1043c serine protease were 9.0 and 45°C, respectively. Moreover, the serine protease activity of Rv1043c was enhanced by divalent metal ions of Ca2+ and Mg2+. Site-directed mutagenesis studies demonstrated that the serine 279 residue in Rv1043c plays a catalytic role. Additionally, mouse model studies confirmed that Rv1043c significantly enhanced the survival of Msg in vivo, induced pulmonary injury and lung cell apoptosis, and promoted the release of pro-inflammatory cytokines interleukin-1β and interleukin-6 in mice. This study presents novel insights into the relationship between mycobacterial serine protease and the pathogenesis of the disease.