The role of the amino-terminal domain and the collagenous region in the structure and the function of rat surfactant protein D.
Surfactant protein D (SP-D) is a member of the C-type lectin superfamily with four distinct structural domains: an amino terminus involved in forming intermolecular disulfides, a collagen-like domain, a neck region, and a carbohydrate recognition domain. A collagen domain deletion mutant (CDM) of SP-D was created by site-directed mutagenesis. A second variant lacking both the amino-terminal region and the collagen-like domain was generated by collagenase treatment and purification of the collagenase-resistant fragment (CRF). The CDM expressed in CHO-K1 cells formed the covalent trimers, but not the noncovalent dodecamers, typical of native SP-D. The CRF derived from recombinant SP-D formed only monomers. The CDM bound mannose-Sepharose and phosphatidylinositol (PI) as well as SP-D, but the binding to mannosyl bovine serum albumin and glucosylceramide was diminished by approximately 60%. The CRF displayed weak binding to mannose-Sepharose and PI and essentially no binding to mannosyl bovine serum albumin and glucosylceramide. Both SP-D and CDM altered the self-aggregation of PI-containing liposomes. SP-D reduced the density and the light scattering properties of PI aggregates. These results demonstrate that the collagen-like domain is required for dodecamer but not covalent trimer formation of SP-D and plays an important, but not essential, role in the interaction of SP-D with PI and GlcCer. Removal of the amino-terminal domain of SP-D along with the collagen-like domain diminishes PI binding and effectively eliminates GlcCer binding.
Ogasawara
Y
Y
Lord and Taylor Laboratory for Lung Biochemistry, National Jewish Center for Immunology and Respiratory Medicine, Denver, Colorado 80206, USA.
Voelker
D R
DR
D000818:Animals; D002118:Calcium / Q000502:physiology; D003094:Collagen / Q000737:chemistry*; D017364:Collagenases / Q000494:pharmacology; D005690:Galactose / Q000378:metabolism; D006017:Glycolipids / Q000378:metabolism; D006023:Glycoproteins / Q000737:chemistry* / Q000502:physiology; D008081:Liposomes / Q000737:chemistry; D008358:Mannose / Q000378:metabolism; D037663:Pulmonary Surfactant-Associated Protein D; D011663:Pulmonary Surfactants / Q000737:chemistry* / Q000502:physiology; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry; D012542:Scattering, Radiation; D013329:Structure-Activity Relationship
D006017:Glycolipids; D006023:Glycoproteins; D008081:Liposomes; D037663:Pulmonary Surfactant-Associated Protein D; D011663:Pulmonary Surfactants; D011994:Recombinant Proteins; D003094:Collagen; D017364:Collagenases; D008358:Mannose; D002118:Calcium; D005690:Galactose