Cystic fibrosis. II. The urinary mucociliary inhibitor

In the current study, the cystic fibrosis cationic mucociliary inhibitor has been purified from urine by ion exchange chromatog-raphy, gel filtration, lectin affinity chromatography, isoelectric focusing, and high performance liquid chromatography. The mo-lecular size of the cationic mucociliary inhibitor was estimated to be in the range of 4,000 to 13,500 MW, by its elution on Sephadex G-50, and between 7,500 and 12,750 MW, by urea-sodium dodecyl sulfate polyacrylamide gel electrophoresis. In addition to the cationic mucociliary inhibitor, an anionic mucociliary inhibitor was also detected in the urinary fraction isoelectrically focused between pH 4.5 and 4.9. The identity of the mucociliary inhibitor as a glycoprotein was established in the current study by affinity chromatography on Phaseolus lunatus lectin, by radiolabeling the carbohydrate with galactose oxidase and tritiated sodium boro- hydride, and by determining the presence of a large concentration of glucosamine and small amounts of galactosamine by amino acid analysis. The amino acio analysis of the purified major component of the cationic mucociliary inhibitor reveals that the glucosamine concentration represents a high percentage of the composition of the glycoprotein. Speculation: The purification of a cationic mucociliary inhibitor from cystic fibrosis urine will facilitate the construction of antibody reagents which can be utilized for feasibility studies of prenatal diagnosis and heterozygote detection.