Heme utilization in Campylobacter jejuni.
A putative iron- and Fur-regulated hemin uptake gene cluster, composed of the transport genes chuABCD and a putative heme oxygenase gene (Cj1613c), has been identified in Campylobacter jejuni NCTC 11168. Mutation of chuA or Cj1613c leads to an inability to grow in the presence of hemin or hemoglobin as a sole source of iron. Mutation of chuB, -C, or -D only partially attenuates growth where hemin is the sole iron source, suggesting that an additional inner membrane (IM) ABC (ATP-binding cassette) transport system(s) for heme is present in C. jejuni. Genotyping experiments revealed that Cj1613c is highly conserved in 32 clinical isolates. One strain did not possess chuC, though it was still capable of using hemin/hemoglobin as a sole iron source, supporting the hypothesis that additional IM transport genes are present. In two other strains, sequence variations within the gene cluster were apparent and may account for an observed negative heme utilization phenotype. Analysis of promoter activity within the Cj1613c-chuA intergenic spacer region revealed chuABCD and Cj1613c are expressed from separate iron-repressed promoters and that this region also specifically binds purified recombinant Fur(Cj) in gel retardation studies. Absorbance spectroscopy of purified recombinant His(6)-Cj1613c revealed a 1:1 heme:His(6)-Cj1613c binding ratio. The complex was oxidatively degraded in the presence of ascorbic acid as the electron donor, indicating that the Cj1613c gene product functions as a heme oxygenase. In conclusion, we confirm the involvement of Cj1613c and ChuABCD in heme/hemoglobin utilization in C. jejuni.
Ridley
Kristian A
KA
Department of Genetics, University of Leicester, Adrian Building, University Road, Leicester LE1 7RH, United Kingdom.
Rock
Jonathan D
JD
Li
Ying
Y
Ketley
Julian M
JM
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport / Q000235:genetics; D002169:Campylobacter Infections / Q000382:microbiology; D016123:Campylobacter jejuni / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D003470:Culture Media; D006418:Heme / Q000378:metabolism*; D006419:Heme Oxygenase (Decyclizing) / Q000235:genetics / Q000378:metabolism*; D006427:Hemin; D006454:Hemoglobins; D006801:Humans; D005810:Multigene Family; D010084:Oxidation-Reduction; D010802:Phylogeny; D011401:Promoter Regions, Genetic / Q000235:genetics; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism
D001426:Bacterial Proteins; D003470:Culture Media; D006454:Hemoglobins; D011956:Receptors, Cell Surface; D006418:Heme; D006427:Hemin; D006419:Heme Oxygenase (Decyclizing)