title: Borrelia burgdorferi RevA antigen is a surface-exposed outer membrane protein whose expression is regulated in response to environmental temperature and pH.
abstract: Borrelia burgdorferi, the causative agent of Lyme disease, produces RevA protein during the early stages of mammalian infection. B. burgdorferi apparently uses temperature as a cue to its location, producing proteins required for infection of warm-blooded animals at temperatures corresponding to host body temperature, but does not produce such virulence factors at cooler, ambient temperatures. We have observed that B. burgdorferi regulates expression of RevA in response to temperature, with the protein being synthesized by bacteria cultivated at 34 degrees C but not by those grown at 23 degrees C. Tissues encountered by B. burgdorferi during its infectious cycle vary in their pH values, and the level of RevA expression was also found to be dependent upon pH of the culture medium. The cellular localization of RevA was also analyzed. Borrelial inner and outer membranes were purified by isopycnic centrifugation, and membrane fractions were conclusively identified by immunoblot analysis using antibodies raised against the integral inner membrane protein MotB and outer membrane-associated Erp lipoproteins. Immunoblot analyses indicated that RevA is located in the B. burgdorferi outer membrane. These analyses also demonstrated that an earlier report (H. A. Bledsoe et al., Infect. Immun. 176:7447-7455, 1994) had misidentified such B. burgdorferi membrane fractions. RevA was further demonstrated to be exposed to the external environment, where it could facilitate interactions with host tissues.
authors.affiliation: Microscopy Branch, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana 59840, USA. jcarroll@niaid.nih.gov
authors.forename: J A
authors.initials: JA
authors.lastname: Carroll
authors.forename: N
authors.initials: N
authors.lastname: El-Hage
authors.forename: J C
authors.initials: JC
authors.lastname: Miller
authors.forename: K
authors.initials: K
authors.lastname: Babb
authors.forename: B
authors.initials: B
authors.lastname: Stevenson
mesh_terms: D000595:Amino Acid Sequence; D000942:Antigens, Bacterial / Q000032:analysis / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics*; D001425:Bacterial Outer Membrane Proteins / Q000032:analysis / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics* / Q000276:immunology; D001426:Bacterial Proteins / Q000378:metabolism; D001483:Base Sequence; D015748:Borrelia burgdorferi Group / Q000254:growth & development / Q000276:immunology* / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D003470:Culture Media; D015964:Gene Expression Regulation, Bacterial; D006863:Hydrogen-Ion Concentration; D015151:Immunoblotting; D008969:Molecular Sequence Data; D017422:Sequence Analysis, DNA; D013696:Temperature
chemical_list: D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D003470:Culture Media; C064779:MotB protein, Bacteria; C434447:RevA protein, Borrelia burgdorferi