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Infection and Immunity, April 2000, p. 1864-1870, Vol. 68, No. 4
Graduate Institute of Microbiology, College
of Medicine, National Taiwan University, Taipei, Taiwan, Republic
of China
Received 27 October 1999/Returned for modification 22 November
1999/Accepted 14 December 1999
The interaction of viridans streptococci with components of the
extracellular matrix (ECM) plays an important role in the pathogenesis
of infective endocarditis. We have identified a surface protein of
Streptococcus mutans which binds the ECM constituent fibronectin (Fn). Initially, we found that S. mutans could
adsorb soluble Fn in plasma, but with lower efficiency than
Streptococcus pyogenes. In addition, S. mutans
could bind immobilized Fn in a dose-dependent manner when tested using
an enzyme-linked immunosorbent assay. Crude extracts of cell
wall-associated proteins or extracellular proteins from S. mutans MT8148 specifically bound Fn through a protein with the
molecular mass of ca. 130 kDa, as detected by far-Western
immunoblotting. The candidate Fn binding protein (FBP-130) was purified
to near homogeneity by using Fn coupled Sepharose 4B affinity column
chromatography. A rabbit polyclonal antibody against FBP-130 reacted
specifically with a protein of molecular mass of ca. 130 kDa in both
cell wall and extracellular fractions, and the abundance of FBP was
higher in the former than in the latter fractions. The purified FBP
bound specifically to immobilized Fn, whereas the binding of soluble Fn
to coated FBP could only be detected in the presence of high
concentrations of Fn. The purified FBP, as well as anti-FBP
immunoglobulin G, inhibited the adherence of S. mutans to
immobilized Fn and endothelial cells (ECV304) in a dose-dependent
manner. These results demonstrated that FBP-130 mediated the adherence
of S. mutans specifically to Fn and endothelial cells in
vitro. The characteristics of S. mutans and FBP-130 in
binding Fn confirmed that viridans streptococci adopt different
strategies in their interaction with ECM.
0019-9567/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Identification of a Fibronectin Binding Protein
from Streptococcus mutans
*
Corresponding author. Mailing address: No. 1, Jen Ai
Road 1st Section, Rm. 713, Graduate Institute of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan. Phone: 886-2-23970800, ext. 8222. Fax: 886-2-23915293. E-mail:
chiajs{at}ha.mc.edu.tw.
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