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Journal of Bacteriology, January 2005, p. 175-184, Vol. 187, No. 1
0021-9193/05/$08.00+0     doi:10.1128/JB.187.1.175-184.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

bdrF₂ of Lyme Disease Spirochetes Is Coexpressed with a Series of Cytoplasmic Proteins and Is Produced Specifically during Early Infection

Hongming Zhang,¹ Abayami Raji,¹ Michael Theisen,² Paul R. Hansen,³ and Richard T. Marconi^1,4*

Department of Microbiology and Immunology,¹ Center for the Study of Biological Complexity,⁴ Medical College of Virginia at Virginia Commonwealth University, Richmond, Virginia, and Department of Infectious Disease Immunology, Statens Serum Institut,² The Royal Veterinary and Agricultural University, Copenhagen, Denmark³

Received 29 June 2004/ Accepted 15 September 2004

The Bdr proteins are polymorphic inner membrane proteins produced by most Borrelia species. In Borrelia burgdorferi B31MI, the18 bdr genes form three subfamilies, bdrD, bdrE, and bdrF. The production of at least one of the Bdr paralogs, BdrF₂, is up-regulated in host-adapted spirochetes, suggesting a role for the protein in the mammalian environment. Here, we demonstrate using reverse transcriptase (RT) PCR that BBG29, BBG30, BBG31, and BBG32, which reside upstream of bdrF₂, are cotranscribed with bdrF₂ as a five-gene operon. While the functions of most of these proteins are unknown, BBG32 encodes a putative DNA helicase. Real-time RT-PCR analyses demonstrated higher levels of bdrF₂ transcript relative to other genes of the operon, suggesting that bdrF₂ may also be transcribed independently from an internal promoter. Internal promoters were detected using the 5' rapid amplification of cDNA ends system. The putative promoter associated with bdrF₂ was found to be highly similar in sequence to the multiple promoters associated with the ospC gene. Real-time RT-PCR analyses, performed to assess the expression of these genes in infected mice, revealed that genes of the bdrF₂ locus are expressed only during early infection, suggesting a role in the establishment of infection. To further characterize the proteins encoded by the bdrF₂ locus, which have unknown functions, the cellular localizations of these proteins were determined by Triton X-114 extraction and phase partitioning. BBG29 and BBG31 were found to be cytoplasmic. To determine if these proteins elicit an antibody (Ab) response during infection, immunoblot analyses were performed. Abs to these proteins were not detected. Based on the analyses presented here, we offer the hypothesis that BdrF₂ and other proteins encoded by the operon form an inner-membrane-associated protein complex that may interact with DNA and which carries out its functional role during transmission or the early stages of infection.

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* Corresponding author. Mailing address: Department of Microbiology and Immunology, Center for the Study of Biological Complexity, Medical College of Virginia at Virginia Commonwealth University, Richmond, Virginia 23298-0678. Phone: (804) 828-3779. Fax: (804) 828-9946. E-mail: rmarconi{at}hsc.vcu.edu.

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Journal of Bacteriology, January 2005, p. 175-184, Vol. 187, No. 1
0021-9193/05/$08.00+0     doi:10.1128/JB.187.1.175-184.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

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