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Infect. Immun., Feb 1997, 412-421, Vol 65, No. 2
P Lahdenne, SF Porcella, KE Hagman, DR Akins, TG Popova, DL Cox, LI Katona, JD Radolf and MV Norgard
Isolated outer membranes of Borrelia burgdorferi 297 were utilized to
obtain partial amino acid sequence information for a low-molecular- weight,
outer membrane-associated polypeptide. Degenerate oligonucleotide primers
based upon this information were used to amplify a 100-bp probe for
detection of the corresponding full-length gene within a B. burgdorferi
total genomic library. The relevant open reading frame (ORF) encoded a
polypeptide comprised of a 17-amino-acid putative signal peptide terminated
by LFVAC, a probable consensus sequence for lipoprotein modification, and a
mature protein of 51 amino acids (predicted molecular mass of 5.8 kDa). The
DNA sequences of the corresponding ORFs in B. burgdorferi 297 and B31 were
identical; the corresponding ORF in strain N40 differed by only one
nucleotide. Assuming conventional processing and acylation, the molecular
weight of the lipoprotein, designated lp6.6, is about 6,600. The lp6.6
gene, which was localized to the 49-kb linear plasmid of B. burgdorferi,
subsequently was cloned and expressed in Escherichia coli as a fusion
protein with glutathione S-transferase. Immunoblot analysis with monoclonal
antibody 240.7 revealed that lp6.6 was identical to a low-
molecular-weight, highly conserved B. burgdorferi lipoprotein reported
previously (L. I. Katona, G. Beck, and G. S. Habicht, Infect. Immun.
60:4995-5003, 1992). Results of indirect immunofluorescence assays, growth
inhibition assays, passive immunizations, and active immunizations
indicated that this outer membrane-associated antigen is not surface
exposed in B. burgdorferi. Particularly interesting was the finding that
mice and rhesus monkeys chronically infected with B. burgdorferi failed to
develop antibodies against this antigen. We propose that high-level
expression of lp6.6 is associated with the arthropod phase of the
spirochetal life cycle and that expression of the gene is downregulated
during mammalian infection.
Copyright © 1997, American Society for Microbiology
Molecular characterization of a 6.6-kilodalton Borrelia burgdorferi outer membrane-associated lipoprotein (lp6.6) which appears to be downregulated during mammalian infection
Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas 75235, USA.
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