The immunoglobulin domain, also known as the immunoglobulin fold, is a type of
protein domain
In molecular biology, a protein domain is a region of a protein's Peptide, polypeptide chain that is self-stabilizing and that Protein folding, folds independently from the rest. Each domain forms a compact folded Protein tertiary structure, thre ...
that consists of a 2-layer sandwich of 7-9
antiparallel β-strands arranged in two
β-sheets with a
Greek key topology,
consisting of about 125 amino acids.
The
backbone switches repeatedly between the two β-sheets. Typically, the pattern is (
N-terminal
The N-terminus (also known as the amino-terminus, NH2-terminus, N-terminal end or amine-terminus) is the start of a protein or polypeptide, referring to the free amine group (-NH2) located at the end of a polypeptide. Within a peptide, the amin ...
β-hairpin in sheet 1)-(β-hairpin in sheet 2)-(β-strand in sheet 1)-(
C-terminal
The C-terminus (also known as the carboxyl-terminus, carboxy-terminus, C-terminal tail, carboxy tail, C-terminal end, or COOH-terminus) is the end of an amino acid chain (protein or polypeptide), terminated by a free carboxyl group (-COOH). When t ...
β-hairpin in sheet 2). The cross-overs between sheets form an "X", so that the N- and C-terminal hairpins are facing each other.
Members of the immunoglobulin superfamily are found in hundreds of proteins of different functions. Examples include
antibodies
An antibody (Ab) or immunoglobulin (Ig) is a large, Y-shaped protein belonging to the immunoglobulin superfamily which is used by the immune system to identify and neutralize antigens such as bacteria and viruses, including those that caus ...
, the giant muscle kinase
titin
Titin (; also called connectin) is a protein that in humans is encoded by the ''TTN'' gene. The protein, which is over 1 μm in length, functions as a molecular spring that is responsible for the passive elasticity of muscle. It comprises 2 ...
, and
receptor tyrosine kinase
Receptor tyrosine kinases (RTKs) are the high-affinity cell surface receptors for many polypeptide growth factors, cytokines, and hormones. Of the 90 unique tyrosine kinase genes identified in the human genome, 58 encode receptor tyrosine kinas ...
s. Immunoglobulin-like domains may be involved in
protein–protein and protein–
ligand
In coordination chemistry, a ligand is an ion or molecule with a functional group that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's el ...
interactions.
Examples
Human genes encoding proteins containing the immunoglobulin domain include:
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A1BG
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ACAM
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ADAMTSL1
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ADAMTSL3
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AGER
Ager or AGER may refer to:
* Ager (surname)
Places
* Ager (river), a river in Upper Austria
* Àger, a municipality in Catalonia, Spain
* Viscounty of Àger, a medieval Catalan jurisdiction that branched off the County of Urgell
* Ager, Californ ...
*
ALCAM
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AMIGO1
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AMIGO2
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AXL
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BCAM
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BOC
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BSG
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BTLA
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C10orf72
*
C20orf102
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CADM1
*
CADM3
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CD200
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CD22
CD22, or cluster of differentiation-22, is a molecule belonging to the SIGLEC family of lectins. It is found on the surface of mature B cells and to a lesser extent on some immature B cells. Generally speaking, CD22 is a regulatory molecule tha ...
*
CD276
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CD33
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CD4
In molecular biology, CD4 (cluster of differentiation 4) is a glycoprotein that serves as a co-receptor for the T-cell receptor (TCR). CD4 is found on the surface of immune cells such as helper T cells, monocytes, macrophages, and dendritic c ...
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CDON
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CEACAM1
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CEACAM16
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CEACAM20
Carcinoembryonic antigen-related cell adhesion molecule 20 is a carcinoembryonic antigen
Carcinoembryonic antigen (CEA) describes a set of highly-related glycoproteins involved in cell adhesion. CEA is normally produced in gastrointestinal tis ...
*
CEACAM21
Carcinoembryonic antigen-related cell adhesion molecule 21 is a carcinoembryonic antigen
Carcinoembryonic antigen (CEA) describes a set of highly-related glycoproteins involved in cell adhesion. CEA is normally produced in gastrointestinal tis ...
*
CEACAM5
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CEACAM6
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CEACAM8
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CHL1
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CILP
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CNTFR
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CNTN1
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CNTN2
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CNTN3
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CNTN4
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CNTN5
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CNTN6
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CSF1R
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DSCAM
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DSCAML1
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EMB
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F11R
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FAIM3
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FCAR
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FCER1A
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FCGR1A
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FCGR2A
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FCGR2B
Fc fragment of IgG receptor IIb (coded by FCGR2B gene) is a low affinity inhibitory receptor for the Fc region of immunoglobulin gamma ( IgG). FCGR2B participates in the phagocytosis of immune complexes and in the regulation of antibody producti ...
*
FCGR2C
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FCGR3A
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FCGR3B
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FCRH1
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FCRH3
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FCRH4
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FCRL1
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FCRL2
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FCRL3
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FCRL4
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FCRL5
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FCRL6
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FCRLA
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FGFR1
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FGFR2
Fibroblast growth factor receptor 2 (FGFR-2) also known as CD332 (cluster of differentiation 332) is a protein that in humans is encoded by the ''FGFR2'' gene residing on chromosome 10. FGFR2 is a receptor for fibroblast growth factor.
FGFR-2 is ...
*
FGFR3
Fibroblast growth factor receptor 3 (FGFR-3) is a protein that in humans is encoded by the ''FGFR3'' gene. FGFR3 has also been designated as CD333 (cluster of differentiation 333). The gene, which is located on chromosome 4, location p16.3, is e ...
*
FGFR4
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FGFRL1
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FLT1
Vascular endothelial growth factor receptor 1 is a protein that in humans is encoded by the ''FLT1'' gene.
Function
''FLT1'' is a member of VEGF receptor gene family. It encodes a receptor tyrosine kinase which is activated by VEGF-A, VEGF-B, ...
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FLT3
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FLT4
Fms-related tyrosine kinase 4, also known as FLT4, is a protein which in humans is encoded by the ''FLT4'' gene.
This gene encodes a tyrosine kinase receptor for vascular endothelial growth factors C and D. The protein is thought to be involv ...
*
FSTL4
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FSTL5
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GP6
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GPA33
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GPR116
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GPR125
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HEPACAM
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HLA-DMA
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HLA-DMB
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HLA-DQB
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HLA-DQB1
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HMCN1
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HNT
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HSPG2
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HYST2477
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ICAM3
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ICAM5
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IGHA1
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IGHD
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IGHE
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IGSF10
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IGSF11
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IGSF2
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IGSF21
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IGSF3
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IGSF9
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IL11RA
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IL1R1
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IL1R2
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IL1RAPL1
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IL1RAPL2
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IL1RL1
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IL1RL2
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IL6R
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JAM2
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JAM3
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KIR-123FM
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KIR2DL1
Killer cell immunoglobulin-like receptor 2DL1 is a protein that in humans is encoded by the ''KIR2DL1'' gene
In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nu ...
*
KIR2DL2
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KIR2DL3
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KIR2DL4
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KIR2DL5A
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KIR2DL5B
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KIR2DLX
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KIR2DS1
Killer cell immunoglobulin-like receptor, two domains, short cytoplasmic tail, 1 is a protein that in humans is encoded by the KIR2DS1 gene
In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The mole ...
*
KIR2DS2
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KIR2DS3
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KIR2DS4
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KIR2DS5
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KIR3DL1
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KIR3DL2
Killer cell immunoglobulin-like receptor 3DL2 is a protein that in humans is encoded by the ''KIR3DL2'' gene.
Structure
Killer cell immunoglobulin-like receptors (KIRs) are transmembrane glycoproteins expressed on natural killer (NK) cells ...
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KIR3DL3
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KIR3DS1
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KIT
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L1CAM
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LAG3
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LILRA1
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LILRA2
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LILRA3
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LILRA4
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LILRA5
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LILRA6
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LILRB1
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LILRB2
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LILRB3
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LILRB4
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LILRB5
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LILRP2
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LRIG1
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LRIG2
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LRIG3
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LRIT1
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LRRC4
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LSAMP
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MAG
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MALT1
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MCAM
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MDGA1
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MDGA2
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MERTK
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MFAP3
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MIR
''Mir'' (, ; ) was a space station operated in low Earth orbit from 1986 to 2001, first by the Soviet Union and later by the Russia, Russian Federation. ''Mir'' was the first modular space station and was assembled in orbit from 1986 to ...
* MIR
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MXRA5
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MYBPC3
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MYOM1
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MYOM3
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NCA
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NCAM1
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NCAM2
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NEGR1
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NEO1
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NFASC
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NOPE
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NPHS1
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NPTN
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NRCAM
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NRG1
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NT
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NTRK3
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OBSCN
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OBSL1
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OPCML
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PAPLN
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PDGFRA
Platelet-derived growth factor receptor A, also termed CD140a, is a Receptor (biochemistry), receptor located on the surface of a wide range of cell types. The protein is encoded in the human by the ''PDGFRA'' gene. This receptor binds to certain ...
*
PDGFRB
Platelet-derived growth factor receptor beta is a protein that in humans is encoded by the ''PDGFRB'' gene. Mutations in PDGFRB are mainly associated with the clonal eosinophilia class of malignancies.
Gene
The ''PDGFRB'' gene is located on h ...
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PDGFRL
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PECAM1
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PRODH2
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PSG1
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PSG10
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PSG11
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PSG11s'
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PSG2
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PSG3
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PSG4
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PSG5
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PSG6
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PSG7
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PSG8
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PSG9
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PTGFRN
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PTK7
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PTPRD
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PTPRK
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PTPRM
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PTPRS
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PTPsigma
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PUNC
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PVR
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PVRL1
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PVRL2
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PVRL4
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RAGE
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SCN1B
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SDK1
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SDK2
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SEMA3A
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SEMA3B
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SEMA3E
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SEMA3F
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SEMA3G
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SEMA4D
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SIGLEC1
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SIGLEC10
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SIGLEC11
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SIGLEC12
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SIGLEC14
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SIGLEC6
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SIGLEC7
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SIGLEC8
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SIRPG
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THY1
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TIE1
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TMIGD1
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TMIGD2
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TTN
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TYRO3
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UNC5D
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VCAM1
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VSIG1
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VSIG2
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VSIG4
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hEMMPRIN
*
kir3d
See also
*
Immunoglobulin superfamily
The immunoglobulin superfamily (IgSF) is a large protein superfamily of cell surface and soluble proteins that are involved in the recognition, binding, or adhesion processes of cells. Molecules are categorized as members of this superfamily ...
References
External links
SCOP listing of immunoglobulin domains of known structure
{{Protein tertiary structure
Protein domains
Protein folds
Single-pass transmembrane proteins