Recombinant human SP-A1 and SP-A2 proteins have different carbohydrate-binding characteristics.
Surfactant protein (SP)-A is a member of the collectin family of proteins and plays a role in innate host defense of the lung. SP-A binds to the carbohydrates of lung pathogens via its calcium-dependant carbohydrate-binding domain. Native human alveolar SP-A consists of two distinct gene products: SP-A1 and SP-A2; however, only SP-A2 is expressed in the submucosal glands of the conducting airways. The function of the isolated SP-A2 protein is unknown. We hypothesized that SP-A1 and SP-A2 might have different carbohydrate-binding properties. In this study, we characterized the carbohydrate-binding specificities of native human alveolar SP-A and recombinant human SP-A1 and SP-A2 in the presence of either 1 or 5 mM Ca(2+). We found that all of the SP-A proteins bind carbohydrates but with different affinities. All of the SP-A proteins bind to fucose with the greatest affinity. SP-A2 binds with a higher affinity to a wider variety of sugars than SP-A1 at either 1 or 5 mM Ca(2+). These findings are suggestive that SP-A2 may interact with a greater variety of pathogens than native SP-A.
Oberley
Rebecca E
RE
Department of Anatomy and Cell Biology, University of Iowa College of Medicine, Iowa City, Iowa 52242, USA.
Snyder
Jeanne M
JM
D000581:Amidohydrolases / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D050260:Carbohydrate Metabolism; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007313:Insecta; D008970:Molecular Weight; D043524:Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase; D011485:Protein Binding; D037662:Pulmonary Surfactant-Associated Protein A / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012685:Sepharose / Q000378:metabolism
D037662:Pulmonary Surfactant-Associated Protein A; D011994:Recombinant Proteins; C445842:SFTPA1 protein, human; C445843:SFTPA2 protein, human; D012685:Sepharose; D000581:Amidohydrolases; D043524:Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase; D002118:Calcium