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3370  structures 3474  species 70  interactions 136715  sequences 4292  architectures

Clan: Ig (CL0011)


Immunoglobulin superfamily Add an annotation

Members of the immunoglobulin superfamily are found in hundreds of proteins of different functions. Examples include antibodies, the giant muscle kinase titin and receptor tyrosine kinases. Immunoglobulin-like domains may be involved in protein-protein and protein-ligand interactions. The superfamily can be divided into discrete structural sets, by the presence or absence of beta-strands in the structure and the length of the domains [1]. Proteins containing domains of the C1 and V-sets are mostly molecules of the vertebrate immune system. Proteins of the C2-set are mainly lymphocyte antigens, this differs from the composition of the C2-set as originally proposed [1]. The I-set is intermediate in structure between the C1 and V-sets and is found widely in cell surface proteins as well as intracellular muscle proteins.

This clan contains 24 families and the total number of domains in the clan is 136715. The clan was built by A Bateman and RD Finn.

Literature references

  1. Williams AF, Barclay AN; , Annu Rev Immunol 1988;6:381-405.: The immunoglobulin superfamily--domains for cell surface recognition. PUBMED:3289571 EPMC:3289571
  2. Harpaz Y, Chothia C; , J Mol Biol 1994;238:528-539.: Many of the immunoglobulin superfamily domains in cell adhesion molecules and surface receptors belong to a new structural set which is close to that containing variable domains. PUBMED:8176743 EPMC:8176743


This clan contains the following 24 member families:

A2M Adeno_E3_CR1 Adhes-Ig_like C1-set C2-set C2-set_2 Herpes_gE Herpes_gI Herpes_glycop_D I-set ICAM_N ig Ig_2 Ig_3 Ig_Tie2_1 IZUMO K1 Lep_receptor_Ig Marek_A PTCRA Receptor_2B4 SVA V-set V-set_CD47

External database links

Domain organisation

Below is a listing of the unique domain organisations or architectures from this clan. More...

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The table below shows the number of occurrences of each domain throughout the sequence database. More...

Pfam family Num. domains Alignment
I-set (PF07679) 59728 (43.7%) View
Ig_2 (PF13895) 24350 (17.8%) View
V-set (PF07686) 19537 (14.3%) View
C1-set (PF07654) 16594 (12.1%) View
Ig_3 (PF13927) 4712 (3.4%) View
C2-set_2 (PF08205) 3971 (2.9%) View
A2M (PF00207) 2819 (2.1%) View
ig (PF00047) 1594 (1.2%) View
K1 (PF02960) 847 (0.6%) View
Herpes_gE (PF02480) 334 (0.2%) View
C2-set (PF05790) 320 (0.2%) View
Lep_receptor_Ig (PF06328) 304 (0.2%) View
Herpes_glycop_D (PF01537) 286 (0.2%) View
Pfam family Num. domains Alignment
Marek_A (PF02124) 236 (0.2%) View
ICAM_N (PF03921) 218 (0.2%) View
Adeno_E3_CR1 (PF02440) 217 (0.2%) View
Herpes_gI (PF01688) 161 (0.1%) View
IZUMO (PF15005) 129 (0.1%) View
V-set_CD47 (PF08204) 126 (0.1%) View
SVA (PF05326) 63 (0.0%) View
Ig_Tie2_1 (PF10430) 53 (0.0%) View
Receptor_2B4 (PF11465) 44 (0.0%) View
Adhes-Ig_like (PF09085) 43 (0.0%) View
PTCRA (PF15028) 29 (0.0%) View
Total: 24 Total: 136715 Clan alignment

Please note: Clan alignments can be very large and can cause problems for some browsers. Read the note above before viewing.

Family relationships

This diagram shows the relationships between members of this clan. More...

Species distribution

Tree controls


This tree shows the occurrence of the domains in this clan across different species. More...



For those sequences which have a structure in the Protein DataBank, we use the mapping between UniProt, PDB and Pfam coordinate systems from the MSD group, to allow us to map Pfam domains onto UniProt three-dimensional structures. The table below shows the mapping between the Pfam families in this clan, the corresponding UniProt entries, and the region of the three-dimensional structures that are available for that sequence.

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