Human surfactant protein D: SP-D contains a C-type lectin carbohydrate recognition domain.
Lung surfactant protein D (SP-D) shows calcium-dependent binding to specific saccharides, and is similar in domain structure to certain members of the calcium-dependent (C-type) lectin family. Using a degenerate oligomeric probe corresponding to a conserved peptide sequence derived from the amino-terminus of the putative carbohydrate binding domain of rat and bovine SP-D, we screened a human lung cDNA library and isolated a 1.4-kb cDNA for the human protein. The relationship of the cDNA to SP-D was established by several techniques including amino-terminal microsequencing of SP-D-derived peptides, and immunoprecipitation of translation products of transcribed mRNA with monospecific antibodies to SP-D. In addition, antibodies to a synthetic peptide derived from a predicted unique epitope within the carbohydrate recognition domain of SP-D specifically reacted with SP-D. DNA sequencing demonstrated a noncollagenous carboxy-terminal domain that is highly homologous with the carboxy-terminal globular domain of previously described C-type lectins. This domain contains all of the so-called "invariant residues," including four conserved cysteine residues, and shows high homology with the mannose-binding subfamily of C-type lectins. Sequencing also demonstrated an amino-terminal collagenous domain that contains an uninterrupted sequence of 59 Gly-X-Y triplets and that also contains the only identified consensus for asparagine-linked oligosaccharides. The studies demonstrate that SP-D is a member of the C-type lectin family, and confirm predicted structural similarities to conglutinin, SP-D, and the serum mannose binding proteins.
Rust
K
K
Department of Pathology, Jewish Hospital, Washington University Medical Center, St. Louis, Missouri 63110.
Grosso
L
L
Zhang
V
V
Chang
D
D
Persson
A
A
Longmore
W
W
Cai
G Z
GZ
Crouch
E
E
D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites; D050260:Carbohydrate Metabolism; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics; D006023:Glycoproteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D037102:Lectins / Q000378:metabolism; D008969:Molecular Sequence Data; D037663:Pulmonary Surfactant-Associated Protein D; D011663:Pulmonary Surfactants / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
D006023:Glycoproteins; D037102:Lectins; D037663:Pulmonary Surfactant-Associated Protein D; D011663:Pulmonary Surfactants; D004247:DNA