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200  structures 430  species 0  interactions 5320  sequences 538  architectures

Family: Pentaxin (PF00354)

Summary: Pentaxin family

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This is the Wikipedia entry entitled "Pentraxins". More...

Pentraxins Edit Wikipedia article

The pentraxins are a family of proteins characterised by calcium dependant ligand binding and a distinctive flattened β-jellyroll structure similar to that of the legume lectins (Emsley J. et al, 1994). The name "pentraxin" is derived from the Greek word for five (penta) and berries (ragos) relating to the radial symmetry of five monomers forming a ring approximately 95Å across and 35Å deep. The "short" pentraxins include Serum Amyloid P component (SAP) and C reactive protein (CRP). The "long" pentraxins include PTX3 (a cytokine modulated molecule) and several neuronal pentraxins.

CRP drawn from PDB: 1B09​.


Emsley, J., White, H.E., O’Hara, B.P., Oliva, G., Srinivasan, N., Tickle, I.J., Blundell, T.L., Pepys, M.B. and Wood S.P. (1994) Structure of pentameric human serum amyloid P component. Nature 367:338-345

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.

Pentaxin family Provide feedback

Pentaxins are also known as pentraxins.

Literature references

  1. Gewurz H, Zhang XH, Lint TF; , Curr Opin Immunol 1995;7:54-64.: Structure and function of the pentraxins. PUBMED:7772283 EPMC:7772283

  2. Srinivasan N, White HE, Emsley J, Wood SP, Pepys MB, Blundell TL; , Structure 1994;2:1017-1027.: Comparative analyses of pentraxins: implications for protomer assembly and ligand binding. PUBMED:7881902 EPMC:7881902

  3. Emsley J, White HE, O'Hara BP, Oliva G, Srinivasan N, Tickle IJ, Blundell TL, Pepys MB, Wood SP; , Nature 1994;367:338-345.: Structure of pentameric human serum amyloid P component. PUBMED:8114934 EPMC:8114934

Internal database links

External database links

This tab holds annotation information from the InterPro database.

InterPro entry IPR001759

This entry represents Pentaxins and its related proteins such as CRP (C-reactive protein) and SAP (serum amyloid P component protein) [ PUBMED:9480764 ]. This entry also includes adhesion G-protein coupled receptors D2 and G6 from humans.

Pentraxins (or pentaxins) [ PUBMED:6356809 , PUBMED:7772283 ] are a family of proteins which show, under electron microscopy, a discoid arrangement of five noncovalently bound subunits. Proteins of the pentraxin family are involved in acute immunological responses [ PUBMED:7772283 ]. Three of the principal members of the pentraxin family are serum proteins and Ca 2 dependent: namely, C-reactive protein (CRP) [ PUBMED:9614930 ], serum amyloid P component protein (SAP) [ PUBMED:9514915 ], and female protein (FP) [ PUBMED:9583999 ]. CRP binds to ligands containing phosphocholine, SAP binds to amyloid fibrils, DNA, chromatin, fibronectin, C4-binding proteins and glycosaminoglycans.

CRP is expressed during acute phase response to tissue injury or inflammation in mammals. The protein resembles antibody and performs several functions associated with host defence: it promotes agglutination, bacterial capsular swelling and phagocytosis, and activates the classical complement pathway through its calcium-dependent binding to phosphocholine. CRPs have also been sequenced in an invertebrate, Limulus polyphemus (Atlantic horseshoe crab), where they are a normal constituent of the hemolymph [ PUBMED:7881902 ].

SAP is a vertebrate protein that is a precursor of amyloid component P. It is found in all types of amyloid deposits, in glomerular basement menbrane and in elastic fibres in blood vessels. SAP binds to various lipoprotein ligands in a calcium-dependent manner, and it has been suggested that, in mammals, this may have important implications in atherosclerosis and amyloidosis [ PUBMED:8114934 ].

FP is a SAP homologue found in Mesocricetus auratus (golden hamster). The concentration of this plasma protein is altered by sex steroids and stimuli that elicit an acute phase response.

"Long" pentraxins have N-terminal extensions to the common pentraxin domain [ PUBMED:8899296 ]; one group, the neuronal pentraxins, may be involved in synapse formation and remodeling, and they may also be able to form heteromultimers [ PUBMED:10748068 ]. Pentraxin proteins expressed in the nervous system are neural pentraxin I (NPI) and II (NPII) [ PUBMED:8884281 ]. NPI and NPII are homologous and can exist within one species. It is suggested that both proteins mediate the uptake of synaptic macromolecules and play a role in synaptic plasticity. Apexin, a sperm acrosomal protein, is a homologue of NPII found in Cavia porcellus (Guinea pig) [ PUBMED:7798266 ].

PTX3 is a long pentraxin that provides defence against infectious agents and plays several functions in tissue repair and regulation of cancer-related inflammation [ PUBMED:31019517 ].

Domain organisation

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You can also download a FASTA format file containing the full-length sequences for all sequences in the full alignment.

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HMM logos is one way of visualising profile HMMs. Logos provide a quick overview of the properties of an HMM in a graphical form. You can see a more detailed description of HMM logos and find out how you can interpret them here. More...


This page displays the phylogenetic tree for this family's seed alignment. We use FastTree to calculate neighbour join trees with a local bootstrap based on 100 resamples (shown next to the tree nodes). FastTree calculates approximately-maximum-likelihood phylogenetic trees from our seed alignment.

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Curation and family details

This section shows the detailed information about the Pfam family. You can see the definitions of many of the terms in this section in the glossary and a fuller explanation of the scoring system that we use in the scores section of the help pages.

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Seed source: Prosite
Previous IDs: pentaxin;
Type: Domain
Sequence Ontology: SO:0000417
Author: Finn RD
Number in seed: 8
Number in full: 5320
Average length of the domain: 185 aa
Average identity of full alignment: 26 %
Average coverage of the sequence by the domain: 22.7 %

HMM information View help on HMM parameters

HMM build commands:
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 61295632 -E 1000 --cpu 4 HMM pfamseq
Model details:
Parameter Sequence Domain
Gathering cut-off 25.0 25.0
Trusted cut-off 25.0 25.0
Noise cut-off 24.9 24.9
Model length: 194
Family (HMM) version: 20
Download: download the raw HMM for this family

Species distribution

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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 Pentaxin domain has been found. There are 200 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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AlphaFold Structure Predictions

The list of proteins below match this family and have AlphaFold predicted structures. Click on the protein accession to view the predicted structure.

Protein Predicted structure External Information
A0A0G2JST1 View 3D Structure Click here
A0A0G2JZ18 View 3D Structure Click here
A0A0R4IAT2 View 3D Structure Click here
A0A140LGW6 View 3D Structure Click here
A0A2R8QS39 View 3D Structure Click here
A3KPG7 View 3D Structure Click here
A3KPH5 View 3D Structure Click here
A3KPH6 View 3D Structure Click here
A3KPH7 View 3D Structure Click here
A3KPH8 View 3D Structure Click here
A3KPN2 View 3D Structure Click here
A3KPN4 View 3D Structure Click here
A8MV57 View 3D Structure Click here
C6KFA3 View 3D Structure Click here
D2D0C1 View 3D Structure Click here
D3YYJ7 View 3D Structure Click here
D3ZT94 View 3D Structure Click here
E7F742 View 3D Structure Click here
E7F744 View 3D Structure Click here
E9QD28 View 3D Structure Click here
F1Q4P1 View 3D Structure Click here
F1Q689 View 3D Structure Click here
F1RAX6 View 3D Structure Click here
O19062 View 3D Structure Click here
O19063 View 3D Structure Click here
O35764 View 3D Structure Click here
O70340 View 3D Structure Click here
O95502 View 3D Structure Click here
P02741 View 3D Structure Click here
P02742 View 3D Structure Click here
P02743 View 3D Structure Click here
P07629 View 3D Structure Click here
P12246 View 3D Structure Click here
P14847 View 3D Structure Click here
P23680 View 3D Structure Click here
P26022 View 3D Structure Click here
P47970 View 3D Structure Click here
P47971 View 3D Structure Click here
P47972 View 3D Structure Click here
P48199 View 3D Structure Click here