Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Pivot Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Target Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Query: EC:3.5.1.52 (
PNGase F
)
1,527
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
The dominant form of human
surfactant protein D
(
SP-D
) is a multimeric collagenous glycoprotein composed of monomeric subunits that have a molecular mass of 43 kDa under reducing conditions. However, in evaluating monoclonal antibodies to human
SP-D
, an additional monomeric subunit was identified with a reduced molecular mass of 50 kDa. This 50-kDa variant was detected in approximately half of the samples evaluated and was found in lavage fluid from normal subjects, patients with alveolar proteinosis or idiopathic pulmonary fibrosis and in amniotic fluid. This 50-kDa variant had the same amino-terminal sequence, amino acid composition and apparent size of the carboxy-terminal collagenase-resistant fragment (20 kDa) as the 43-kDa subunit. The major difference was in the amino-terminal portion of the molecule and was due to altered glycosylation, as determined by carbohydrate staining, chemical deglycosylation, treatment with
N-glycanase
and neuraminidase and reduced signals for threonine at positions 5, 9 and 10 during amino-terminal sequencing. After gel filtration chromatography, the 50-kDa form was not present in the high molecular weight fraction, which is commonly used in purification of
SP-D
, but was found only in the smaller molecular weight fraction of monomers and trimers of
SP-D
. In conclusion, the 50 kDa-form of
surfactant protein D
is produced by post-translational glycosylation and does not form higher ordered oligomers, but its precise physiological function remains to be determined.
...
PMID:A 50-kDa variant form of human surfactant protein D. 986 12
Pulmonary
surfactant protein D
(
SP-D
) is a member of the collectin family and plays crucial roles in the innate immunity of the lung. We have previously shown that surfactant protein A (SP-A), a homologous collectin, interacts with MD-2 and alters lipopolysaccharide signaling. In this study, we examined and characterized the binding of
SP-D
to MD-2 using a soluble form of recombinant MD-2 (sMD-2).
SP-D
bound in a concentration- and Ca(2+)-dependent manner to sMD-2 coated onto microtiter wells. Excess mannose abolished the binding of
SP-D
to sMD-2. In solution,
SP-D
cosedimented with sMD-2 in the presence of Ca(2+). The direct binding of
SP-D
to sMD-2 was confirmed by BIAcore analysis. Anti-
SP-D
monoclonal antibody that recognizes the carbohydrate recognition domain (CRD) of
SP-D
significantly inhibited the binding of
SP-D
to sMD-2, indicating the involvement of the CRD for the binding to sMD-2. Ligand blot analysis revealed that
SP-D
bound to N-
glycopeptidase
F-treated sMD-2. In addition, the biotinylated
SP-D
pulled down the mutant sMD-2 with Asn(26) --> Ala and Asn(114) --> Ala substitutions, which lacks the consensus for N-glycosylation. Furthermore, the sMD-2 mutant cosedimented
SP-D
. These results demonstrate that
SP-D
directly interacts with MD-2 through the CRD.
...
PMID:Pulmonary surfactant protein D binds MD-2 through the carbohydrate recognition domain. 1899 97
