Identification and characterization of a mitochondrial iron-superoxide dismutase of Cryptosporidium parvum.

Cryptosporidium parvum is an intracellular protozoan parasite that causes cryptosporidiosis in mammals. In this study, we identified a gene encoding mitochondrial iron-superoxide dismutase of C. parvum (Cp-mtSOD) and characterized biochemical properties of the recombinant protein. Multiple sequence alignment of the deduced amino acid sequence of Cp-mtSOD with those of previously reported iron-containing SODs (Fe-SODs) from other protozoan parasites showed that Cp-mtSOD shares common metal-binding residues and motifs that were conserved in Fe-SODs. However, the N-terminal 26-amino acid residues of Cp-mtSOD did not show sequence identities to any other Fe-SOD sequences. Further analysis of the N-terminal presequence of Cp-mtSOD suggested that it shares common physiochemical characteristics found in mitochondria targeting sequences and predicted localization of Cp-mtSOD in the mitochondria. The recombinant Cp-mtSOD showed typical biochemical properties with other characterized Fe-SODs, including molecular structure, broad pH optimum, and sensitivity to hydrogen peroxide.