Characterization of the collagen- and non-collagen-like regions present in a glycoprotein isolated from alveoli of patients with alveolar proteinosis.

A major glycoprotein of Mr 36 000 has been isolated from the lung lavage of patients with alveolar proteinosis and found to contain five residues of hydroxyproline, 50 residues of glycine, 2.6 mol of sialic acid, 4.8 mol of mannose, 4.1 mol of galactose, 0.9 mol of fucose, 7.0 mol of N-acetylglucosamine. Limited pepsin digestion of this glycoprotein resulted in six peptides, three of which contained hydroxyproline and nearly 30% glycine and two of which contained all the carbohydrate present in the native glycoprotein. All three peptides containing hydroxyproline and high content of glycine were found to contain -Gly-x-y-Gly- type sequences. Partial amino acid sequence analyses indicate that this glycoprotein is composed of alternating short collagen- and non-collagen-like peptide sequences.