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106  structures 98  species 0  interactions 202  sequences 12  architectures

Family: Surfac_D-trimer (PF09006)

Summary: Lung surfactant protein D coiled-coil trimerisation

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This is the Wikipedia entry entitled "Pulmonary surfactant protein D". More...

Pulmonary surfactant protein D Edit Wikipedia article

PDB 2os9 EBI.jpg
crystal structure of the trimeric neck and carbohydrate recognition domain of human surfactant protein d in complex with myoinositol

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]


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]


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].


  1. ^ 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.
  2. ^ 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.
  3. ^ 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.
  4. ^ 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.
This article incorporates text from the public domain Pfam and InterPro: IPR015097

This page is based on a Wikipedia article. The text is available under the Creative Commons Attribution/Share-Alike License.

This tab holds the annotation information that is stored in the Pfam database. As we move to using Wikipedia as our main source of annotation, the contents of this tab will be gradually replaced by the Wikipedia tab.

Lung surfactant protein D coiled-coil trimerisation Provide feedback

This domain, predominantly found in lung surfactant protein D, forms a triple-helical parallel coiled coil, and mediates trimerisation of the protein [1].

Literature references

  1. Kovacs H, O'Ddonoghue SI, Hoppe HJ, Comfort D, Reid KB, Campbell D, Nilges M; , J Biomol NMR. 2002;24:89-102.: Solution structure of the coiled-coil trimerization domain from lung surfactant protein D. PUBMED:12495025 EPMC:12495025

This tab holds annotation information from the InterPro database.

InterPro entry IPR015097

This domain is found in the SFTPD family, which includes lung surfactant protein D (SFTPD), conglutinin, collectin-43 and collectin-46. It forms a triple-helical parallel coiled coil, and mediates trimerisation of the protein [ PUBMED:12495025 ].

Domain organisation

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Curation and family details

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Curation View help on the curation process

Seed source: pdb_1m7l
Previous IDs: none
Type: Coiled-coil
Sequence Ontology: SO:0001080
Author: Mistry J , Sammut SJ
Number in seed: 5
Number in full: 202
Average length of the domain: 44.00 aa
Average identity of full alignment: 56 %
Average coverage of the sequence by the domain: 13.24 %

HMM information View help on HMM parameters

HMM build commands:
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 57096847 -E 1000 --cpu 4 HMM pfamseq
Model details:
Parameter Sequence Domain
Gathering cut-off 20.7 20.7
Trusted cut-off 20.7 20.9
Noise cut-off 20.5 20.6
Model length: 46
Family (HMM) version: 13
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Species distribution

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Archea Archea Eukaryota Eukaryota
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For those sequences which have a structure in the Protein DataBank, we use the mapping between UniProt, PDB and Pfam coordinate systems from the PDBe group, to allow us to map Pfam domains onto UniProt sequences and three-dimensional protein structures. The table below shows the structures on which the Surfac_D-trimer domain has been found. There are 106 instances of this domain found in the PDB. Note that there may be multiple copies of the domain in a single PDB structure, since many structures contain multiple copies of the same protein sequence.

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