Heme uptake is a common means of iron and porphyrin acquisition by many pathogenic bacteria. The genus Haemophilus includes several important pathogenic bacterial species that characteristically require hemin-, protoporphyrin-, or heme-substituted proteins as essential growth factors under aerobic conditions. However, the mechanism of heme transport is not understood for Haemophilus. We have cloned a DNA fragment from H. influenzae that allows an Escherichia coli hemA mutant to employ exogenous hemin or protoporphyrin IX as sole sources of porphyrin. DNA sequencing of the cloned DNA fragment suggested that a previously characterized gene (hel) encoding an antigenic, outer membrane lipoprotein e(P4) was responsible for the complementation activity. Construction of hel insertion mutations in strain H. influenzae Rd demonstrated that hel is essential for growth under aerobic conditions but not under anaerobic conditions. The aerobic growth defect of hel mutants could be reversed by providing exogenous hemin in the presence of outer membrane. The analysis of hybrids between e(P4) and beta-lactamase demonstrated that a domain of e(P4) near its NH2' terminus was required for its function in hemin use. Within this domain is a short amino acid sequence that displays similarity to H. influenzae hemin binding protein HbpA, hemin-binding motifs present in eukaryotic transcription activator heme-activated protein, and the heme containing proteins hemoglobin (alpha-chain) and cytochrome C3, suggesting that this region may be involved in hemin binding and/or transport.
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February 01 1996
Lipoprotein e(P4) is essential for hemin uptake by Haemophilus influenzae.
J Reidl,
J Reidl
Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA.
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J J Mekalanos
J J Mekalanos
Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA.
Search for other works by this author on:
J Reidl
Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA.
J J Mekalanos
Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA.
Online ISSN: 1540-9538
Print ISSN: 0022-1007
J Exp Med (1996) 183 (2): 621–629.
Citation
J Reidl, J J Mekalanos; Lipoprotein e(P4) is essential for hemin uptake by Haemophilus influenzae.. J Exp Med 1 February 1996; 183 (2): 621–629. doi: https://doi.org/10.1084/jem.183.2.621
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