In vitro sulfation of pulmonary surfactant-associated protein-35.
Surfactant-associated protein-35 consists of a group of phospholipid-associated proteins of 26-36 kDa isolated from pulmonary alveolar surfactant. In the rat, surfactant-associated protein-35 is synthesized from 26-kDa primary translation products which are cotranslationally acetylated and glycosylated to heterogeneous 30 and 34 kDa forms. High-mannose oligosaccharide-containing precursors of surfactant-associated protein-35 are processed in the rough endoplasmic reticulum and Golgi to complex-type oligosaccharides, resulting in a mature glycoprotein which exhibits extensive charge heterogeneity in two-dimensional isoelectric focusing SDS-polyacrylamide gel electrophoresis. Much of this charge heterogeneity is related to terminal sialylation of the two asparagine-linked oligosaccharides. In the present study, we report that surfactant-associated protein-35 is also sulfated. Sulfation of the 30 and 34 kDa forms of surfactant-associated protein-35 was clearly detected in primary cultures of rat Type II epithelial cells. These sulfated isoforms were sensitive to endoglycosidase F digestion, but resistant to neuraminidase, suggesting that sulfation occurred at oligosaccharide residues other than sialic acid. The lack of sulfation of the 26 kDa forms of surfactant-associated protein-35 and the resistance of the sulfated isoforms to endoglycosidase H digestion are consistent with Golgi-associated sulfation of the complex type oligosaccharides of surfactant-associated protein-35. Thus, sulfation is another component of the complex post-translational processing of surfactant-associated protein-35, which includes acetylation, hydroxylation, glycosylation, sialylation, sulfhydryl-dependent oligomerization and sulfation.
D000818:Animals; D002478:Cells, Cultured; D004848:Epithelium / Q000378:metabolism; D006023:Glycoproteins / Q000235:genetics*; D007700:Kinetics; D008297:Male; D008970:Molecular Weight; D011499:Protein Processing, Post-Translational; D011510:Proteolipids / Q000096:biosynthesis / Q000235:genetics* / Q000302:isolation & purification; D011650:Pulmonary Alveoli / Q000378:metabolism*; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants / Q000096:biosynthesis / Q000235:genetics* / Q000302:isolation & purification; D051381:Rats; D011919:Rats, Inbred Strains; D013431:Sulfates / Q000378:metabolism; D013462:Sulfur Radioisotopes
D006023:Glycoproteins; D011510:Proteolipids; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants; D013431:Sulfates; D013462:Sulfur Radioisotopes