Fibronectin‐binding proteins of Clostridium perfringens recognize the III1‐C fragment of fibronectin

The Clostridium perfringens strain 13 genome contains two genes (fbpA, fbpB) that encode putative Fbp. Both rFbpA and rFbpB were purified and their reactivity with human serum Fn was analyzed. To determine the region of the Fn molecule recognized by rFbp, a plate binding assay using N‐terminal 70‐kDa peptide, III₁‐C peptide, and 110‐kDa peptide containing III_2–10 of Fn was performed. Both rFbp bound to the III₁‐C peptide of Fn but not to the other peptides. However, the III₁‐C fragment of Fn is known to be cryptic in serum Fn. Then, rFbp‐BP from Fn were purified by rFbp‐affinity chromatography. The yield of purified proteins was approximately 1% of the applied Fn on a protein basis. Western blotting analysis of the rFbp‐BP, using four different anti‐Fn monoclonal antibodies, revealed that the rFbp‐BP carried partial Fn antigenicity. Bindings of rFbp to rFbp‐BP were inhibited by the presence of the III₁‐C peptide, suggesting that rFbp‐BP express the III₁‐C fragment. The binding of Fn to III₁‐C was inhibited by the presence of either rFbpA or rFbpB. This result that suggests C. perfringens Fbps may inhibit the formation of Fn‐matrix in vivo.