A detailed analysis will be performed of the glycoprotein components of respiratory mucus. The major secretory macromolecule is responsible for maintenance of the reheologic properties of the mucus and apparently provides a vehicle whereby airway lipid components may be passively cleaned from the respiratory tract. Purification of the glycoprotein can be achieved by taking advantage of its high molecular weight (exclusion chromatography) and high buoyant density (density gradient centrifugation). Lipid removal by solvent extraction yields substantially homogeneous preparations from which the saccharide components can be completely removed by alkali catalyzed elimination in the presence of sodium borohydride. The oligosaccharides are clustered along the polypeptide chain and range in the size from 2-14 sugars. The attachment is via galactosamine to seryl or threonyl residues which comprise approximately one-half of the amino acids in the sugar rich domain. The macrostructure of the glycoprotein is maintained, in part, by disulfide cross links whose cleavage results in a substantial reduction in molecular weight. Lipid binding specificity and stoichiometry as well as the role of the disulfide bridges in exhibited physical properties will be examined.
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