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38  structures 468  species 0  interactions 33237  sequences 934  architectures

Family: SRCR (PF00530)

Summary: Scavenger receptor cysteine-rich domain

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This is the Wikipedia entry entitled "Scavenger receptor cysteine-rich protein domain". More...

Scavenger receptor cysteine-rich protein domain Edit Wikipedia article

PDB 1by2 EBI.jpg
structure of m2bp scavenger receptor cysteine-rich domain
Symbol SRCR
Pfam PF00530
InterPro IPR001190
SCOP 1by2

In molecular biology, the protein domain SRCR is short for Scavenger receptor cysteine-rich domain. They are found solely in eukaryotes. These domains are present on the cell membrane and have a role in binding to specific ligands and are often found to be involved with the immune system.[1]


The function of these endocytic receptors are to mediating non-opsonic phagocytosis in response to foreign ligands. This triggers various processes of host defence and immune response.[2]


The structure contains a six stranded beta-sheet and one alpha-helix.[1]


The speract receptor found in egg, is a transmembrane glycoprotein.[3] Other members of this family include the macrophage scavenger receptor type I, an enteropeptidase, and T-cell surface glycoprotein CD5.


  1. ^ a b Hohenester E; Sasaki T; Timpl R (1999). "Crystal structure of a scavenger receptor cysteine-rich domain sheds light on an ancient superfamily.". Nat Struct Biol. 6 (3): 228–32. PMID 10074941. doi:10.1038/6669. 
  2. ^ Liu L, Yang J, Qiu L, Wang L, Zhang H, Wang M, et al. (2011). "A novel scavenger receptor-cysteine-rich (SRCR) domain containing scavenger receptor identified from mollusk mediated PAMP recognition and binding.". Dev Comp Immunol. 35 (2): 227–39. PMID 20888856. doi:10.1016/j.dci.2010.09.010. 
  3. ^ Resnick D; Pearson A; Krieger M (January 1994). "The SRCR superfamily: a family reminiscent of the Ig superfamily". Trends Biochem. Sci. 19 (1): 5–8. PMID 8140623. doi:10.1016/0968-0004(94)90165-1. 

This article incorporates text from the public domain Pfam and InterPro IPR001190

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Scavenger receptor cysteine-rich domain Provide feedback

These domains are disulphide rich extracellular domains. These domains are found in several extracellular receptors and may be involved in protein-protein interactions.

Literature references

  1. Resnick D, Pearson A, Krieger M; , Trends Biochem Sci 1994;19:5-8.: The SRCR superfamily - A family reminiscent of the Ig superfamily. PUBMED:8140623 EPMC:8140623

  2. Hohenester E, Sasaki T, Timpl R; , Nat Struct Biol 1999;6:228-232.: Crystal structure of a scavenger receptor cysteine-rich domain sheds light on an ancient superfamily. PUBMED:10074941 EPMC:10074941

Internal database links

External database links

This tab holds annotation information from the InterPro database.

InterPro entry IPR001190

The scavenger receptor cysteine-rich (SRCR) domain is an ancient and highly conserved domain of about 110 residues which is found in diverse secreted and cell-surface proteins, like the type I scavenger receptor, the speract receptor, CD5/Ly-1, CD6, or complement factor I [ PUBMED:1978939 ]. Tandem repeats of SRCR domains are common in the membrane bound proteins. Most SRCR domains have six to eight cysteines that participate in intradomain disulfide bonds. SRCR domains have been subdivided into two groups, A and B, primarily on the differences in the spacing pattern between the cysteine residues [ PUBMED:8140623 , PUBMED:10074941 ].

Although the biochemical functions of SRCR domains have not been established with certainty, they are likely to mediate protein-protein interactions and ligand binding [ PUBMED:8140623 , PUBMED:10074941 ].

Determination of the crystal structure of the SRCR domain of M2BP reveals that the M2NP SRCR adopts a compact fold of approximate dimensions 22 x 26 x 30 Angstrom, organised around a curved six-stranded beta-sheet cradling an alpha- helix [ PUBMED:10074941 ].

Gene Ontology

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Domain organisation

Below is a listing of the unique domain organisations or architectures in which this domain is found. More...

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Pfam Clan

This family is a member of clan SRCR (CL0550), which has the following description:

The clan contains the following 3 members:



We store a range of different sequence alignments for families. As well as the seed alignment from which the family is built, we provide the full alignment, generated by searching the sequence database (reference proteomes) using the family HMM. We also generate alignments using four representative proteomes (RP) sets and the UniProtKB sequence database. More...

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We make a range of alignments for each Pfam-A family. You can see a description of each above. You can view these alignments in various ways but please note that some types of alignment are never generated while others may not be available for all families, most commonly because the alignments are too large to handle.

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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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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

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Seed source: Reference [1]
Previous IDs: none
Type: Domain
Sequence Ontology: SO:0000417
Author: Bateman A
Number in seed: 74
Number in full: 33237
Average length of the domain: 96.50 aa
Average identity of full alignment: 35 %
Average coverage of the sequence by the domain: 44.24 %

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 26.1 26.1
Trusted cut-off 26.1 26.1
Noise cut-off 26.0 26.0
Model length: 100
Family (HMM) version: 20
Download: download the raw HMM for this family

Species distribution

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Colour assignments

Archea Archea Eukaryota Eukaryota
Bacteria Bacteria Other sequences Other sequences
Viruses Viruses Unclassified Unclassified
Viroids Viroids Unclassified sequence Unclassified sequence


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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 SRCR domain has been found. There are 38 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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