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 intracellular pathogen Mycobacteriumn avium subspecies paratuberculosis. This led to the identification of sodC, a gene which codes for a copper and zinc 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 overexpressed in Escherichia coli. The renatured, affinity-purified recombinant protein possessed enzymatic activity that was inhibited by the presence of cyanide, which is characteristic of a Cu,ZnSOD.