IDENTIFICATION AND PURIFICATION OF A CONSERVED HEME-REGULATED HEMOGLOBIN-BINDING OUTER-MEMBRANE PROTEIN FROM HAEMOPHILUS-DUCREYI

A hemoglobin-binding protein (HgbA) from Haemophilus ducreyi was ident ified and purified, The 100-kDa HgbA was detected in all strains of H. ducreyi tested, and a somewhat larger hemoglobin-binding protein was found in one strain of Haemophilus influenzae. HgbA was purified and t he amino acid sequence of the N terminus of HgbA revealed no significa nt homologies with known proteins, Two different antisera to HgbA from H. ducreyi 35000 recognized HgbA proteins from all tested H. ducreyi strains; they did not recognize proteins from the H. influenzae strain , Expression of HgbA was regulated by the level of heme but not by iro n present in the medium. Animal species of hemoglobin competed with io dinated human hemoglobin for binding to whole cells of H. ducreyi and supported the growth of H. ducreyi, The lack of immunological cross-re activity and the differences in hemoglobin specificities between the H . ducreyi and the H. influenzae hemoglobin-binding proteins suggest th at they are unrelated.