Characterization of Integral Membrane Proteins in Borrelia burgdorferi

Lyme disease (LD) is the most prevalent arthropod-borne infectious disease in the US accounting for approximately 300,000 cases, according to the Centers for Disease Control and Prevention. The agent of LD is the spirochetal pathogen Borrelia burgdorferi (Bb), which has very unique membrane architecture. The genome of Bb encodes for a large open reading frame -BB0512- , which encodes of a protein with a predicted molecular weight of 254 kDa. In silico analysis of this protein indicated that BB0512 is unique to many spirochetal pathogens as well as mycoplasma, with no significant homology to membrane proteins in other prokaryotes. Additionally, BB0512 also contains a reticulocyte binding/rhoptry protein, which is important for red blood cell (RBC) invasion in P. falciparum, P. yoelii domain [3]. Hence, BB0512 could play an important role in the patho-physiology of many spirochetal diseases. In order to further evaluate the role of this protein, we have over-expressed and purified both a full-length and truncated protein, lacking the N-terminal region. Immunoblot analysis revealed the synthesis of bb0512 in protein lysates of Bb propagated under both fed and un-fed tick conditions. We are in the process of generating a deletion mutant of BB0512 and aim to determine the role of this protein in the infectious process of Bb. The genome of Bb encodes another open reading frame, -BB0725- which encodes an integral membrane protein that contains a conserved domain typical of lectins. In addition, in silico analysis revealed a conserved TrkA domain, typically found in the TrkA potassium transporter system. Trk/Ktr/HKT superfamily of ion transporters are crucial in bacteria and play a role in resistance to osmotic stress and high salinity by mediating early uptake of potassium ions (K+) [4, 5]. We have over-expressed and purified 725 and used the antigen to generate polyclonal antisera in mice in an effort to characterize this novel protein and determine its role in the patho-physiology of Bb. We believe that a greater understanding of the organization of the spirochetal cell wall will have a significant impact on developing methods to reduce the number of cases of LD.