The iron-binding protein Dps confers hydrogen peroxide stress resistance to Campylobacter jejuni.
We identified and characterized the iron-binding protein Dps from Campylobacter jejuni. Electron microscopic analysis of this protein revealed a spherical structure of 8.5 nm in diameter, with an electron-dense core similar to those of other proteins of the Dps (DNA-binding protein from starved cells) family. Cloning and sequencing of the Dps-encoding gene (dps) revealed that a 450-bp open reading frame (ORF) encoded a protein of 150 amino acids with a calculated molecular mass of 17,332 Da. Amino acid sequence comparison indicated a high similarity between C. jejuni Dps and other Dps family proteins. In C. jejuni Dps, there are iron-binding motifs, as reported in other Dps family proteins. C. jejuni Dps bound up to 40 atoms of iron per monomer, whereas it did not appear to bind DNA. An isogenic dps-deficient mutant was more vulnerable to hydrogen peroxide than its parental strain, as judged by growth inhibition tests. The iron chelator Desferal restored the resistance of the Dps-deficient mutant to hydrogen peroxide, suggesting that this iron-binding protein prevented generation of hydroxyl radicals via the Fenton reaction. Dps was constitutively expressed during both exponential and stationary phase, and no induction was observed when the cells were exposed to H(2)O(2) or grown under iron-supplemented or iron-restricted conditions. On the basis of these data, we propose that this iron-binding protein in C. jejuni plays an important role in protection against hydrogen peroxide stress by sequestering intracellular free iron and is expressed constitutively to cope with the harmful effect of hydrogen peroxide stress on this microaerophilic organism without delay.
Ishikawa
Takahiko
T
Department of Bacteriology, Internal Medicine, Faculty of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan.
Mizunoe
Yoshimitsu
Y
Kawabata
Shun-ichiro
S
Takade
Akemi
A
Harada
Mine
M
Wai
Sun Nyunt
SN
Yoshida
Shin-ichi
S
D001426:Bacterial Proteins / Q000502:physiology*; D016123:Campylobacter jejuni / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D003001:Cloning, Molecular; D003676:Deferoxamine / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D033862:Iron-Binding Proteins / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D009154:Mutation
D001426:Bacterial Proteins; D033862:Iron-Binding Proteins; D006861:Hydrogen Peroxide; D003676:Deferoxamine