Corynebacterium diphtheriae genes required for acquisition of iron from haemin and haemoglobin are homologous to ABC haemin transporters.
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.
Drazek
E S
ES
Laboratory of Bacterial Toxins, Division of Bacterial Products, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, Maryland 20892, USA.
Hammack
C A
CA
Schmitt
M P
MP
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
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