The sodA gene of Haemophilus ducreyi encodes a hydrogen peroxide-inhibitable superoxide dismutase.

Haemophilus ducreyi is the etiologic agent of the sexually transmitted disease chancroid, an ulcerative condition implicated in increased HIV transmission. There is increasing evidence for the roles of oxidative stress proteins including superoxide dismutase enzymes in the survival and persistence of pathogenic organisms within the host. The sodA gene of Haemophilus ducreyi was isolated from a genomic plasmid library on the basis of its ability to rescue the hydrogen peroxide hypersensitivity of an Escherichia coli sodA sodB strain. The H. ducreyi SodA protein also complemented the aerobic growth defect of the E. coli sodA sodB strain in minimal medium. The deduced amino-acid sequence of the H. ducreyi sodA gene product is 74 and 70% identical to the Mn-SODs of Haemophilus influenzae and E. coli, respectively. However, unlike Mn-SODs, the H ducreyi SodA protein was inhibited by hydrogen peroxide in native gels stained for SOD activity.