Isolation and Characterization of a Unique Glycoprotein from Lavage of Chicken Lungs and Lamellar Organelles

A major glycoprotein with an estimated molecular weight by sodium dodecylsulfate-acrylamide gel electrophoresis of 36,000 daltons has been found in lavage material of normal chicken lung. Amino acid and carbohydrate analyses of this glycoprotein indicated the presence of hydroxyproline, a high percentage of glycine, sialic acid, mannose, galactose, fucose, and glucosamine. Threonine is the NH2-terminal residue of the glycoprotein. A similar glycoprotein of the same molecular weight, NH2-terminus, amino acid, and carbohydrate composition has been found in lamellar organelles isolated from normal chicken lung. The data indicate that this unique collagen-like glycoprotein, which is similar to a major alveolar glycoprotein found in mammals, including patients with alveolar proteinosis, is also a major protein of avian airways. Because avian airways contain no Clara, ciliated, or goblet cells but do contain type II cells as the only secretory airway cells with lamellar organelles, it is likely that in birds this glycoprotein may be a product of type II cells.