Role of SodC in heme acquisition in Haemophilus ducreyi

Abstract

Haemophilus ducreyi expresses outer-membrane receptors for both heme (TdhA) and hemoglobin (HgbA), but no mechanism yet has been identified for the transport of heme from the periplasm to the cytoplasm. SodC protein in H. ducreyi binds to heme in addition to exhibiting superoxide dismutase activity. We hypothesized that SodC is involved in heme uptake in H. ducreyi. An isogenic H. ducreyi sodC mutant was constructed. The generation time of the sodC mutant was increased compared to the wild type strain (35000). The mutant was complemented in trans with either wild type sodC (sod+heme+), sodCH86E with wild type dismutase activity but less heme binding activity (sod+heme-) or with sodCL81FH82QD83G with diminished dismutase activity but wild type heme binding activity (sod-heme+). The generation times of the complemented strains showed no significant difference when grown under limited heme concentration. We conclude that SodC is unlikely to be involved in heme uptake in H. ducreyi.