Corynebacterium diphtheriae genes required for acquisition of iron from haemin and haemoglobin are homologous to ABC haemin transporters

Mol Microbiol. 2000 Apr;36(1):68-84. doi: 10.1046/j.1365-2958.2000.01818.x.


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.

MeSH terms

  • ATP-Binding Cassette Transporters / biosynthesis
  • ATP-Binding Cassette Transporters / genetics*
  • Amino Acid Sequence
  • Bacterial Proteins / genetics
  • Biological Transport
  • Chromosomes, Bacterial / genetics
  • Corynebacterium diphtheriae / genetics*
  • DNA, Bacterial / genetics
  • Escherichia coli / genetics
  • Genes, Bacterial*
  • Genetic Complementation Test
  • Heme Oxygenase (Decyclizing)*
  • Hemin / metabolism*
  • Hemoglobins / metabolism*
  • Iron / metabolism*
  • Lipoproteins / genetics
  • Models, Biological
  • Molecular Sequence Data
  • Mutation
  • Recombinant Proteins / biosynthesis
  • Restriction Mapping
  • Sequence Homology, Amino Acid
  • Species Specificity


  • ATP-Binding Cassette Transporters
  • Bacterial Proteins
  • DNA, Bacterial
  • Hemoglobins
  • HmuT protein, Corynebacterium diphtheriae
  • Lipoproteins
  • Recombinant Proteins
  • Hemin
  • Iron
  • Heme Oxygenase (Decyclizing)
  • HmuO protein, bacteria