Infection and Immunity, April 2000, p. 1884-1892, Vol. 68, No. 4
0019-9567/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Department of Microbiology and Immunology1 and Department of Oral Biological and Medical Sciences,2 University of British Columbia, Vancouver, Canada
Received 29 September 1999/Returned for modification 24 November 1999/Accepted 13 December 1999
Proteins secreted or exported by Treponema denticola
have been implicated as mediators of specific interactions between the spirochete and subgingival tissues in periodontal diseases. However, limited information is available on the ability of this peptidolytic organism to bind or transport soluble peptides present in the subgingival environment. A prominent 70-kDa protein was isolated from
surface extracts of T. denticola ATCC 35405. A clone
expressing a portion of the protein was identified in an
Escherichia coli expression library of T. denticola DNA. DNA sequence analysis showed that the cloned gene
encoded a peptide homologous to OppA, the solute binding protein of an
ATP-binding cassette-type peptide transporter involved in peptide
uptake and environmental signaling in a wide range of bacteria. Genes
encoding OppB, -C, -D, and -F were identified directly downstream of
oppA in T. denticola. OppA was present in
representative strains of T. denticola and in
Treponema vincentii but was not detected in Treponema
pectinovorum or Treponema socranskii. Immunogold
electron microscopy suggested that OppA was accessible to proteins at
the surface of the spirochete. Native OppA bound soluble plasminogen
and fibronectin but did not bind to immobilized substrates or
epithelial cells. A T. denticola oppA mutant bound reduced
amounts of soluble plasminogen, and plasminogen binding to the parent
strain was inhibited by the lysine analog
-aminocaproic acid.
Binding of soluble host proteins by OppA may be important both for
spirochete-host interactions in the subgingival environment and for
uptake of peptide nutrients.
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