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]
| 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 | ||||||||
| |||||||||
Function edit
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 edit
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 edit
- ^ Kovacs H, O'Ddonoghue SI, Hoppe HJ, Comfort D, Reid KB, Campbell D, Nilges M (October 2002). "Solution structure of the coiled-coil trimerization domain from lung surfactant protein D". Journal of Biomolecular NMR. 24 (2): 89–102. doi:10.1023/A:1020980006628. PMID 12495025. S2CID 36593945.
- ^ Zhang P, McAlinden A, Li S, Schumacher T, Wang H, Hu S, et al. (June 2001). "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. doi:10.1074/jbc.M100597200. PMID 11279100.
- ^ Kishore U, Greenhough TJ, Waters P, Shrive AK, Ghai R, Kamran MF, et al. (March 2006). "Surfactant proteins SP-A and SP-D: structure, function and receptors". Molecular Immunology. 43 (9): 1293–315. doi:10.1016/j.molimm.2005.08.004. PMID 16213021.
- ^ Guo CJ, Atochina-Vasserman EN, Abramova E, Foley JP, Zaman A, Crouch E, et al. (November 2008). "S-nitrosylation of surfactant protein-D controls inflammatory function". PLOS Biology. 6 (11): e266. doi:10.1371/journal.pbio.0060266. PMC 2581630. PMID 19007302.