Studies on the carbohydrate-binding characteristics of human pulmonary surfactant-associated protein A and comparison with two other collectins: mannan-binding protein and conglutinin.
The surfactant-associated protein A (SP-A) belongs to the collectin family, a group of C-type lectins encompassing also surfactant-associated protein D, mannan-binding protein (MBP) and conglutinin. These proteins all have carbohydrate-recognition domains joined to collagen stalks. It seems likely that SP-A, like MBP and conglutinin, may mediate anti-microbial activity through binding to carbohydrates on the microorganisms and collectin receptors on phagocytic cells. We have studied the influence of carbohydrates on the binding of SP-A, MBP and conglutinin to mannan in an enzyme-linked lectin-binding assay. All sugars were of D-configuration, except fucose of which both L- and D-configurations were tested. The order of inhibiting potency on the binding of SP-A was: N-acetylmannosamine > L-fucose, maltose > glucose > mannose. The following sugars were non-inhibitory: galactose, D-fucose, glucosamine, mannosamine, galactosamine, N-acetylglucosamine, and N-acetylgalactosamine. The best inhibitor of MBP was N-acetylglucosamine. Otherwise MBP showed a selectivity similar to that of SP-A. Conglutinin binding was inhibited by all the sugars examined except N-acetylgalactosamine. For conglutinin, as for MBP, the best inhibitor was N-acetylglucosamine. Normal human SP-A, alveolar-proteinosis SP-A purified by ion-exchange chromatography, and alveolar-proteinosis SP-A purified by n-butanol extraction showed no difference in sugar selectivity. The influence of pH and of the calcium concentration was also examined. Organic solvent-extracted SP-A from patients suffering from alveolar proteinosis and normal SP-A showed different sensitivity profiles.
Haurum
J S
JS
Department of Immunology, University of Aarhus, Denmark.
Thiel
S
S
Haagsman
H P
HP
Laursen
S B
SB
Larsen
B
B
Jensenius
J C
JC
D000918:Antibody Specificity; D001665:Binding Sites; D050260:Carbohydrate Metabolism; D002352:Carrier Proteins / Q000378:metabolism*; D037222:Collectins; D006023:Glycoproteins / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D037102:Lectins / Q000378:metabolism*; D011510:Proteolipids / Q000276:immunology / Q000378:metabolism*; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants / Q000276:immunology / Q000378:metabolism*; D012712:Serum Globulins / Q000378:metabolism*
D002352:Carrier Proteins; D037222:Collectins; D006023:Glycoproteins; D037102:Lectins; D011510:Proteolipids; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants; D012712:Serum Globulins; C024014:conglutinin