Loss of the ciliary inhibitory effect of the cystic fibrosis factor following proteolytic digestion and heat denaturation

The ciliary inhibitor synthesized by fibroblasts derived from cystic fibrosis patients was subjected to proteolytic digestion and heat denaturation. The fraction from fibroblast media containing the ciliary inhibitor was obtained from chromatography on DEAE at pH 8.5. Following digestion with pepsin at pH 3.9 and with papain at pH 8.5, the media fraction no longer inhibited ciliary activity on oyster gills. Experiments were conducted so that cleaved fragments produced by proteolysis or chemical disruption would not be lost. Following exposure to heat, the media fraction failed to inhibit ciliary activity. These data provide additional evidence that the cystic fibrosis ciliary inhibitor is a protein or a protein complex.