Identification, cloning and expression of sodC from an alkaline phosphatase gene fusion library of Mycobacterium avium subspecies paratuberculosis

The phoA gene technology was used to investigate secreted proteins of the i ntracellular pathogen Mycobacteriumn avium subspecies paratuberculosis. Thi s led to the identification of sodC, a gene which codes for a copper and zi nc cofactored superoxide dismutase (Cu,ZnSOD) which has been implicated as a virulence factor for some pathogens. The predicted protein possessed a 76 % identity with Cu,ZnSOD of Mycobacterium tuberculosis. To characterize Cu, ZnSOD from M. avium subspecies paratuberculosis, the gene was cloned and ov erexpressed in Escherichia coil. The renatured, affinity-purified recombina nt protein possessed enzymatic activity that was inhibited by the presence of cyanide, which is characteristic,of a Cu,ZnSOD.