Biology:Pulmonary surfactant protein D
| Surfac_D-trimer | |||||||||
|---|---|---|---|---|---|---|---|---|---|
 Crystal structure of the trimeric neck and carbohydrate recognition domain of human surfactant protein D in complex with myoinositol | |||||||||
| Identifiers | |||||||||
| Symbol | Surfac_D-trimer | ||||||||
| Pfam | PF09006 | ||||||||
| InterPro | IPR015097 | ||||||||
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In molecular biology, Pulmonary surfactant protein D (SP-D) is a protein domain predominantly found in lung surfactant. This protein plays a special role; its primary task is to act as a defence protein against any pathogens that may invade the lung. It also plays a role in lubricating the lung and preventing it from collapse. It has an interesting structure as it forms a triple-helical parallel coiled coil, helps the protein to fold into a trimer.[1]
Function
Pulmonary surfactant protein D (SP-D), has an important role in acting as a lung host defence protein. SP-D has a significant roles in immune and inflammatory regulation of the lung as it regulates of the level of surfactant in the lungs by a process named surfactant homeostasis.[2]
Structure
SP-D is a type of lectin, more specifically they are a collagen-containing C-type (calcium dependent) lectin which are named collectins. The collectins are responsible for immune and inflammatory control. They have a very basic structure,
- triple-helical collagen region
- C-terminal homotrimeric lectin or carbohydrate recognition domain (CRD).
SP-D is actually a monomer, these monomers assist in high affinity saccharide binding. Three of the same type of monomers associate to form a homotrimer.[3]
SP-D has a complex quaternary structure in which monomers (43 kDa) are assembled into tetramers of trimers thus forming dodecamers. Dodecamers are further assembled into large multimeric structures. The oligomerization of SP-D results in the burial of the tail domains while the head domains are exposed. Oligomerization is dependent upon the cysteine residues at positions 15 and 20 within the N-terminal tail region.[4]
References
- ↑ "Solution structure of the coiled-coil trimerization domain from lung surfactant protein D". Journal of Biomolecular NMR 24 (2): 89–102. October 2002. doi:10.1023/A:1020980006628. PMID 12495025.
- ↑ "The amino-terminal heptad repeats of the coiled-coil neck domain of pulmonary surfactant protein d are necessary for the assembly of trimeric subunits and dodecamers". The Journal of Biological Chemistry 276 (23): 19862–70. June 2001. doi:10.1074/jbc.M100597200. PMID 11279100.
- ↑ "Surfactant proteins SP-A and SP-D: structure, function and receptors". Molecular Immunology 43 (9): 1293–315. March 2006. doi:10.1016/j.molimm.2005.08.004. PMID 16213021.
- ↑ "S-nitrosylation of surfactant protein-D controls inflammatory function". PLOS Biology 6 (11): e266. November 2008. doi:10.1371/journal.pbio.0060266. PMID 19007302.
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