Characterization of a 130,000-dalton glycoprotein isolated from pulmonary secretions of patients with alveolar proteinosis

The proteins of human lung surfactant

Human pulmonary surfactant was purified from bronchoalveolar lavage of patients. The proteins present in surfactant were analyzed by SDS-polyacrylamide gel electrophoresis into serum and non-serum components. One non-serum surfactant protein (Mr = 43 000) was then identified in the 100 000 X g supernatant of a lung homogenate on the basis of phospholipid binding. This lung protein was purified and partially characterized. The presence of 3-methyl histidine and reaction in Western blot analysis with antibody against chicken muscle actin both strongly suggested that the 43 000 Da protein of human surfactant is indeed cytoplasmic actin. It is proposed that this surfactant protein is involved in the secretion and not necessarily in the function of surfactant.

Characterization of two glycoproteins isolated from lung lavage fluid of normal human and from patients with two pulmonary diseases

Two glycoproteins of Mr 62,000 and 36,000 have been isolated and purified from lung lavage of normal human and patients with sarcoidosis and bibasilar fibrosis. The two glycoproteins contained hydroxyproline, high amounts of glycine, and other amino acids in amounts comparable to those present in the same two glycoproteins isolated from lung lavage of patients with alveolar proteinosis. The antibody raised against the glycoprotein of Mr 36,000 isolated from lung lavage material of patients with alveolar proteinosis reacted with both the glycoproteins isolated from normal human as well as from patients with sarcoidosis and bibasilar fibrosis, indicating that these glycoproteins isolated from different sources are structurally related to each other.

Alveolyn--structure and source: a review

Alveolyn is a unique secretory glycoprotein of 250,000 molecular weight (MW) that is found in distal pulmonary secretions. Several glycoproteins of 130,000 MW, 80,000 MW, 62,000 MW, and 36,000 MW have also been found to be present in the alveolar secretions, and it was found that these glycoproteins were proteolytic fragments of the much larger molecular glycoprotein. It is also a major protein in human amniotic fluid, presumably a product of alveolar secretions. It is also secreted by a clone of pulmonary fetal type II cells. Preliminary results indicate that two of the proteolytic fragments of 62,000 MW and 36,000 MW contain alternate collagenous and noncollagenous domains in the same polypeptide chain. The presence of collagenous domains in these glycoproteins was also confirmed by their susceptibility to digestion with collagenase and the presence of Gly-Pro-Hyp-Gly-type sequence in the peptide chain. Very little is known about the tertiary structure of the protein, except that its fragments bind phospholipids and probably facilitate transfer of the lipid to air-water interfaces.

Isolation, characterization and localization of a 45 000 molecular weight, soluble glycoprotein from the lung in pulmonary alveolar proteinosis

A carbohydrate-rich, water-soluble glycoprotein has been isolated in pure form from delipidated lung lavage fluid from a patient with pulmonary alveolar proteinosis, in a three-step procedure involving ion-exchange and gel filtration chromatography. The molecular weight of the glycoprotein was determined to be 45 900 by sedimentation equilibrium analysis in the analytical ultracentrifuge and 45 000 by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, indicating a single polypeptide chain. Nearly half of the mass of the glycoprotein is comprised of carbohydrate that is contributed by 24 residues sialic acid, 23 residues N-acetylglucosamine, 6 residues N-acetylgalactosamine, 19 residues galactose, 4 residues mannose, 1 residue fucose and 1 residue glucose per mol. Unlike a number of collagen-related glycoproteins that have been isolated by others from insoluble lung contents in pulmonary proteinosis, the water-soluble glycoprotein described in the present report does not contain hydroxyproline or hydroxylysine and contains less than 10% of its amino acid residues as glycine. Using rabbit antibodies directed against our purest preparation of material and an immunoperoxidase staining procedure, the 45 000 molecular weight glycoprotein was localized to the thin film of fluid lining the surfaces of alveoli in normal human lungs.