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Journal of Bacteriology, November 2008, p. 7035-7042, Vol. 190, No. 21
0021-9193/08/$08.00+0 doi:10.1128/JB.00818-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Department of Biotechnology, Biocenter, University of Würzburg, Würzburg, Germany,1 Department of Molecular Biology, Umeå University, Umeå, Sweden,2 Rudolf-Virchow-Center, DFG-Research Center for Experimental Biomedicine, University of Würzburg, Würzburg, Germany,3 University of East London, School of Health and Bioscience, Stratford, London, United Kingdom,4 Unité des Rickettsies, CNRS UMR 6020, IFR 48, Université de la Méditerranée, Marseille, France,5 Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana 59840,6 Max-Planck Institute of Biochemistry, Martinsried, Germany7
Received 10 June 2008/ Accepted 18 August 2008
Relapsing fever is a worldwide, endemic disease caused by several spirochetal species belonging to the genus Borrelia. During the recurring fever peaks, borreliae proliferate remarkably quickly compared to the slow dissemination of Lyme disease Borrelia and therefore require efficient nutrient uptake from the blood of their hosts. This study describes the identification and characterization of the first relapsing fever porin, which is present in the outer membranes of B. duttonii, B. hermsii, B. recurrentis, and B. turicatae. The pore-forming protein was purified by hydroxyapatite chromatography and designated Oms38, for outer membrane-spanning protein of 38 kDa. Biophysical characterization of Oms38 was done by using the black lipid bilayer method, demonstrating that Oms38 forms small, water-filled channels of 80 pS in 1 M KCl that did not exhibit voltage-dependent closure. The Oms38 channel is slightly selective for anions and shows a ratio of permeability for cations over anions of 0.41 in KCl. Analysis of the deduced amino acid sequences demonstrated that Oms38 contains an N-terminal signal sequence which is processed under in vivo conditions. Oms38 is highly conserved within the four studied relapsing fever species, sharing an overall amino acid identity of 58% and with a strong indication for the presence of amphipathic β-sheets.
Published ahead of print on 29 August 2008.
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