FIG. 4.

Mucinolytic activity of the 116-kDa secreted protein. (A) Zones of mucin lysis on bovine submaxillary mucin are visible after treatment with Pic protein and staining with amido black (left). No lysis was visible in the section treated with similar preparations of the Pic protein containing a mutation in the serine protease active site (S258I) (right). (B) SDS-PAGE analysis of untreated crude mouse mucus (lane 1) and mucus treated with Pic protein (lane 2). The gel is PAS stained, and the band which is cleaved is indicated, as are the positions of some molecular mass markers. (C) Sephacryl S-400 column chromatography of untreated crude mouse mucus and mucus treated with the concentrated secreted protein. The column was calibrated with dextran blue, and the position of the excluded void volume is indicated. Fractions (0.8 ml) were collected during chromatography. PAS staining was performed on 300-μl aliquots and measured at 555 nm, and the absorbance has been graphed. OD, optical density.