The iron-binding protein dps confers hydrogen peroxide stress resistance to campylobacter jejuni

JOURNAL OF BACTERIOLOGY, Feb. 2003, p. 1010–1017 0021-9193/03/$08.00 0 DOI: 10.1128/JB.185.3.1010–1017.2003 Copyright © 2003, American Society for Microbiology. All Rights Reserved.

Vol. 185, No. 3

The Iron-Binding Protein Dps Confers Hydrogen Peroxide Stress Resistance to Campylobacter jejuni
Takahiko Ishikawa,1,2 Yoshimitsu Mizunoe,1* Shun-ichiro Kawabata,3 Akemi Takade,1 Mine Harada,2 Sun Nyunt Wai,1,4 and Shin-ichi Yoshida1
Department of Bacteriology1 and Department of Medicine and Biosystemic Science, Internal Medicine,2 Faculty of Medical Sciences, and Department of Biology, Faculty of Sciences,3 Kyushu University, Fukuoka 812-8582, Japan, and Department of Molecular Biology, Umea University, S901 87 Umea, Sweden4 ˚ ˚
Received 26 September 2002/Accepted 15 November 2002

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