PMID:16905647

Citation	Létoffé, S, Delepelaire, P and Wandersman, C (2006) The housekeeping dipeptide permease is the Escherichia coli heme transporter and functions with two optional peptide binding proteins. Proc. Natl. Acad. Sci. U.S.A. 103:12891-6
Abstract	Heme, a major iron source, is transported through the outer membrane of Gram-negative bacteria by specific heme/hemoprotein receptors and through the inner membrane by heme-specific, periplasmic, binding protein-dependent, ATP-binding cassette permeases. Escherichia coli K12 does not use exogenous heme, and no heme uptake genes have been identified. Nevertheless, a recombinant E. coli strain expressing just one foreign heme outer membrane receptor can use exogenous heme as an iron source. This result suggests either that heme might be able to cross the cytoplasmic membrane in the absence of specific carrier or that there is a functional inner membrane heme transporter. Here, we show that to use heme iron E. coli requires the dipeptide inner membrane ATP-binding cassette transporter (DppBCDF) and either of two periplasmic binding proteins: MppA, the L-alanyl-gamma-D-glutamyl-meso-diaminopimelate binding protein, or DppA, the dipeptide binding protein. Thus, wild-type E. coli has a peptide/heme permease despite being unable to use exogenous heme. DppA, which shares sequence similarity with the Haemophilus influenzae heme-binding protein HbpA, and MppA are functional heme-binding proteins. Peptides compete with heme for binding both "in vitro" and "in vivo."
Links	PubMed PMC1568943 Online version:10.1073/pnas.0605440103
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Main Points of the Paper

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Materials and Methods Used

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Phenotype Annotations

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Phenotype of	Taxon Information	Genotype Information (if known)	Condition Information	OMP ID	OMP Term Name	ECO ID	ECO Term Name	Notes	Status
a mutation or genetic difference within a strain	Taxon: Escherichia coli Strain: K-12 Substrain: NCBI Taxon ID: 83333	Genotype of Reference Strain: dppB Genotype of Experimental Strain : dppB::Kan in strain JWN3512-2	Reference Condition:					Abolished heme utilization. See table 1.
a mutation or genetic difference within a strain	Taxon: Escherichia coli Strain: K-12 Substrain: NCBI Taxon ID: 83333	Genotype of Reference Strain: dppC Genotype of Experimental Strain : dppC::Kan in strain JWN3511-2	Reference Condition:					Abolished heme utilization. See table 1.
a mutation or genetic difference within a strain	Taxon: Escherichia coli Strain: K-12 Substrain: NCBI Taxon ID: 83333	Genotype of Reference Strain: dppD Genotype of Experimental Strain : dppD::Kan in strain JWN3510-2	Reference Condition:					Abolished heme utilization. See table 1.
a mutation or genetic difference within a strain	Taxon: Escherichia coli Strain: K-12 Substrain: NCBI Taxon ID: 83333	Genotype of Reference Strain: dppF Genotype of Experimental Strain : dppF::Kan in strain JWN3509-2	Reference Condition:					Abolished heme utilization. See table 1.
a mutation or genetic difference within a strain	Taxon: Escherichia coli Strain: K-12 Substrain: NCBI Taxon ID: 83333	Genotype of Reference Strain: dppA mppA Genotype of Experimental Strain : dppA::Kan mppA::Cm	Reference Condition:					Abolished heme utilization. See table 1.
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Notes

OMP: Decrease heme utilization is being made.

ECO: Assay that measured colony size.

References

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