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9417  structures 1365  species 0  interactions 726771  sequences 14368  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 34 families and the total number of domains in the clan is 726771. 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 34 member families:

Adeno_E3_CR1 Adhes-Ig_like bCoV_NS7A bCoV_NS8 C1-set C2-set C2-set_2 CD4-extracel DUF1968 Herpes_gE Herpes_gI Herpes_glycop_D I-set ICAM_N ig Ig_2 Ig_3 Ig_4 Ig_5 Ig_6 Ig_7 Ig_C17orf99 Ig_C19orf38 Ig_Tie2_1 Izumo-Ig K1 Marek_A ObR_Ig PTCRA Receptor_2B4 UL141 V-set V-set_2 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) 379774 (52.3%) View
Ig_3 (PF13927) 144080 (19.8%) View
V-set (PF07686) 91542 (12.6%) View
Ig_2 (PF13895) 28700 (3.9%) View
C1-set (PF07654) 25851 (3.6%) View
ig (PF00047) 22324 (3.1%) View
C2-set_2 (PF08205) 19923 (2.7%) View
Ig_7 (PF19081) 5529 (0.8%) View
Ig_6 (PF18452) 1476 (0.2%) View
ICAM_N (PF03921) 1187 (0.2%) View
Ig_C17orf99 (PF17736) 968 (0.1%) View
ObR_Ig (PF18589) 887 (0.1%) View
C2-set (PF05790) 809 (0.1%) View
V-set_CD47 (PF08204) 536 (0.1%) View
V-set_2 (PF15910) 490 (0.1%) View
Ig_4 (PF16680) 426 (0.1%) View
Receptor_2B4 (PF11465) 413 (0.1%) View
Ig_Tie2_1 (PF10430) 335 (0.0%) View
Pfam family Num. domains Alignment
Ig_5 (PF16681) 294 (0.0%) View
Izumo-Ig (PF16706) 245 (0.0%) View
Ig_C19orf38 (PF17737) 179 (0.0%) View
CD4-extracel (PF09191) 171 (0.0%) View
Adhes-Ig_like (PF09085) 169 (0.0%) View
PTCRA (PF15028) 130 (0.0%) View
DUF1968 (PF09291) 127 (0.0%) View
Herpes_glycop_D (PF01537) 50 (0.0%) View
Marek_A (PF02124) 33 (0.0%) View
Herpes_gE (PF02480) 32 (0.0%) View
Herpes_gI (PF01688) 30 (0.0%) View
Adeno_E3_CR1 (PF02440) 28 (0.0%) View
UL141 (PF16758) 17 (0.0%) View
bCoV_NS7A (PF08779) 7 (0.0%) View
bCoV_NS8 (PF12093) 7 (0.0%) View
K1 (PF02960) 2 (0.0%) View
Total: 34 Total: 726771 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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