title: Corynebacterium diphtheriae genes required for acquisition of iron from haemin and haemoglobin are homologous to ABC haemin transporters.
abstract: Corynebacterium diphtheriae and Corynebacterium ulcerans use haemin and haemoglobin as essential sources of iron during growth in iron-depleted medium. C. diphtheriae and C. ulcerans mutants defective in haemin iron utilization were isolated and characterized. Four clones from a C. diphtheriae genomic library complemented several of the Corynebacteria haemin utilization mutants. The complementing plasmids shared an approximately 3 kb region, and the nucleotide sequence of one of the plasmids revealed five open reading frames that appeared to be organized in a single operon. The first three genes, which we have termed hmuT, hmuU and hmuV, shared striking homology with genes that are known to be required for haemin transport in Gram-negative bacteria and are proposed to be part of an ABC (ATP-binding cassette) transport system. The hmuT gene encodes a 37 kDa lipoprotein that is associated with the cytoplasmic membrane when expressed in Escherichi coli and C. diphtheriae. HmuT binds in vitro to haemin- and haemoglobin-agarose, suggesting that it is capable of binding both haemin and haemoglobin and may function as the haemin receptor in C. diphtheriae. This study reports the first genetic characterization of a transport system that is involved in the utilization of haemin and haemoglobin as iron sources by a Gram-positive bacterium.
authors.affiliation: Laboratory of Bacterial Toxins, Division of Bacterial Products, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, Maryland 20892, USA.
authors.forename: E S
authors.initials: ES
authors.lastname: Drazek
authors.forename: C A
authors.initials: CA
authors.lastname: Hammack
authors.forename: M P
authors.initials: MP
authors.lastname: Schmitt
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000096:biosynthesis / Q000235:genetics*; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics; D001692:Biological Transport; D002876:Chromosomes, Bacterial / Q000235:genetics; D003353:Corynebacterium diphtheriae / Q000235:genetics*; D004269:DNA, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D006419:Heme Oxygenase (Decyclizing); D006427:Hemin / Q000378:metabolism*; D006454:Hemoglobins / Q000378:metabolism*; D007501:Iron / Q000378:metabolism*; D008074:Lipoproteins / Q000235:genetics; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation; D011994:Recombinant Proteins / Q000096:biosynthesis; D015183:Restriction Mapping; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity
chemical_list: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D006454:Hemoglobins; C408133:HmuT protein, Corynebacterium diphtheriae; D008074:Lipoproteins; D011994:Recombinant Proteins; D006427:Hemin; D007501:Iron; D006419:Heme Oxygenase (Decyclizing); C104107:HmuO protein, bacteria