Binding of heme-hemopexin complexes by soluble HxuA protein allows utilization of this complexed heme by Haemophilus influenzae.
Utilization of heme-hemopexin as a source of heme by Haemophilus influenzae type b is dependent on expression by this bacterium of the 100-kDa HxuA protein, which is both present on the bacterial cell surface and released into the culture supernatant (L. D. Cope, R. Yogev, U. Muller-Eberhard, and E. J. Hansen, J. Bacteriol. 177:2644-2653, 1995). Radioimmunoprecipitation analysis showed that the soluble HxuA protein present in H. influenzae type b culture supernatant bound heme-hemopexin complexes in solution. An isogenic H. influenzae type b hxuA mutant was unable to utilize soluble heme-hemopexin complexes for growth in vitro unless soluble HxuA protein was provided exogenously. Soluble HxuA protein secreted by a nontypeable H. influenzae strain also allowed growth of this H. influenzae type b hxuA mutant. These results indicated that the heme present in heme-hemopexin complexes is rendered accessible to H. influenzae when these complexes are bound by the soluble HxuA protein.
Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas 75235-9048, USA.
L D
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Cope
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Thomas
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Hrkal
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Hansen
D000818:Animals; D003470:Culture Media; D006193:Haemophilus influenzae / Q000254:growth & development / Q000378:metabolism*; D006418:Heme / Q000378:metabolism*; D051381:Rats; D011956:Receptors, Cell Surface / Q000378:metabolism*; D012995:Solubility
D003470:Culture Media; D011956:Receptors, Cell Surface; C028027:heme receptor; D006418:Heme