title: Functional differences between heme permeases: Serratia marcescens HemTUV permease exhibits a narrower substrate specificity (restricted to heme) than the Escherichia coli DppABCDF peptide-heme permease.
abstract: Serratia marcescens hemTUV genes encoding a potential heme permease were cloned in Escherichia coli recombinant mutant FB827 dppF::Km(pAM 238-hasR). This strain, which expresses HasR, a foreign heme outer membrane receptor, is potentially capable of using heme as an iron source. However, this process is invalidated due to a dppF::Km mutation which inactivates the Dpp heme/peptide permease responsible for heme, dipeptide, and delta-aminolevulinic (ALA) transport through the E. coli inner membrane. We show here that hemTUV genes complement the Dpp permease for heme utilization as an iron source and thus are functional in E. coli. However, hemTUV genes do not complement the Dpp permease for ALA uptake, indicating that the HemTUV permease does not transport ALA. Peptides do not inhibit heme uptake in vivo, indicating that, unlike Dpp permease, HemTUV permease does not transport peptides. HemT, the periplasmic binding protein, binds heme. Heme binding is saturable and not inhibited by peptides that inhibit heme uptake by the Dpp system. Thus, the S. marcescens HemTUV permease and, most likely, HemTUV orthologs present in many gram-negative pathogens form a class of heme-specific permeases different from the Dpp peptide/heme permease characterized in E. coli.
authors.affiliation: Unité des Membranes Bactériennes, Département de Microbiologie Fondamentale et Médicale, Institut Pasteur, CNRS URA 2172, 75724 Paris Cedex 15, France.
authors.forename: Sylvie
authors.initials: S
authors.lastname: Létoffé
authors.forename: Philippe
authors.initials: P
authors.lastname: Delepelaire
authors.forename: Cécile
authors.initials: C
authors.lastname: Wandersman
mesh_terms: D000622:Aminolevulinic Acid / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D004151:Dipeptides / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D005816:Genetic Complementation Test; D006418:Heme / Q000378:metabolism*; D007501:Iron / Q000378:metabolism; D049449:Luminescence; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D012706:Serratia marcescens / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D004151:Dipeptides; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D006418:Heme; D000622:Aminolevulinic Acid; C043912:peptide permease; D007501:Iron