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 polypeptide chain that is self-stabilizing and that folds independently from the rest. Each domain forms a compact folded three-dimensional structure. Many proteins consist of ...

that consists of a 2-layer sandwich of 7-9 antiparallel β-strands arranged in two

β-sheets The beta sheet, (β-sheet) (also β-pleated sheet) is a common motif of the regular protein secondary structure. Beta sheets consist of beta strands (β-strands) connected laterally by at least two or three backbone hydrogen bonds, forming a gen ...

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 β-hairpin in sheet 1)-(β-hairpin in sheet 2)-(β-strand in sheet 1)-(C-terminal 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), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of ...

, the giant muscle kinase

titin Titin (contraction for Titan protein) (also called connectin) is a protein that in humans is encoded by the ''TTN'' gene. Titin is a giant protein, greater than 1 µm in length, that functions as a molecular spring that is responsible for th ...

, 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 kin ...

s. Immunoglobulin-like domains may be involved in protein–protein and protein–

ligand In coordination chemistry, a ligand is an ion or molecule (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 elect ...

interactions.

Examples

Human genes encoding proteins containing the immunoglobulin domain include: * A1BG * ACAM * ADAMTSL1 * ADAMTSL3 * AGER *

ALCAM CD166 antigen is a 100-105 kD typeI transmembrane glycoprotein that is a member of the immunoglobulin superfamily of proteins. In humans it is encoded by the ''ALCAM'' gene. It is also called CD166 (cluster of differentiation 166), MEMD, SC-1/DM-G ...

* AMIGO1 *

AMIGO2 Amigo(s) (Portuguese and Spanish for ''male friend'') may refer to: People * Carlos Amigo Vallejo (born 1934), Spanish Roman Catholic archbishop emeritus of Seville Places Facilities * Amigos School, a bilingual primary school in Cambridge, Ma ...

* AXL * BCAM * BOC * BSG *

BTLA B- and T-lymphocyte attenuator or BTLA (also known as cluster of differentiation 272 or CD272) is a protein that belongs to the CD28 immunoglobulin superfamily (IgSF) which is encoded by the BTLA gene located on the 3rd human chromosome. BTLA was f ...

C10orf72 C1, C01, C.I or C-1 may refer to: Arts and media * C1, a note-octave in music * C1 Television, a Mongolian television channel * Schecter C-1 Hellraiser FR, a guitar model * A Yamaha grand piano model * "C1", a slang expression in the video game ...

C20orf102 C, or c, is the third letter in the Latin alphabet, used in the modern English alphabet, the alphabets of other western European languages and others worldwide. Its name in English is ''cee'' (pronounced ), plural ''cees''. History "C" ...

* CADM1 * CADM3 *

CD200 OX-2 membrane glycoprotein, also named CD200 (Cluster of Differentiation 200) is a human protein encoded by the gene. The protein encoded by this gene is a type-1 membrane glycoprotein, which contains two immunoglobulin domains, and thus belon ...

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 that ...

CD276 Cluster of Differentiation 276 (CD276) or B7 Homolog 3 (B7-H3) is a human protein encoded by the gene. Structure B7-H3 is a 316 amino acid-long type I transmembrane protein, existing in two isoforms determined by its extracellular domain. In ...

CD33 CD33 or Siglec-3 (sialic acid binding Ig-like lectin 3, SIGLEC3, SIGLEC-3, gp67, p67) is a transmembrane receptor expressed on cells of myeloid lineage. It is usually considered myeloid-specific, but it can also be found on some lymphoid cells. ...

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 T helper cells, monocytes, macrophages, and dendritic ce ...

* CDON *

CEACAM1 Carcinoembryonic antigen-related cell adhesion molecule 1 (biliary glycoprotein) (CEACAM1) also known as CD66a (Cluster of Differentiation 66a), is a human glycoprotein, and a member of the carcinoembryonic antigen (CEA) gene family. Function ...

* CEACAM16 * CEACAM20 * CEACAM21 * CEACAM5 * CEACAM6 * CEACAM8 *

CHL1 Neural cell adhesion molecule L1-like protein also known as close homolog of L1 (CHL1) is a protein that in humans is encoded by the ''CHL1'' gene. CHL1 is a cell adhesion molecule closely related to the L1 (protein), L1. In melanocytic cells CHL ...

* CILP * CNTFR * CNTN1 *

CNTN2 Contactin-2 is a protein that in humans is encoded by the ''CNTN2'' gene. Function The protein encoded by this gene is a member of the immunoglobulin superfamily. It is a glycosylphosphatidylinositol (GPI)-anchored neuronal membrane protein t ...

CNTN3 Contactin-3 is a protein that in humans is encoded by the ''CNTN3'' gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ...

* CNTN4 * CNTN5 *

CNTN6 Contactin 6 is a protein in humans that is encoded by the CNTN6 gene. The protein encoded by this gene is a member of the immunoglobulin superfamily. It is a glycosylphosphatidylinositol Glycosylphosphatidylinositol (), or glycophosphatidylino ...

CSF1R Colony stimulating factor 1 receptor (CSF1R), also known as macrophage colony-stimulating factor receptor (M-CSFR), and CD115 (Cluster of Differentiation 115), is a cell-surface protein encoded by the human ''CSF1R'' gene (known also as c-FMS). C ...

* DSCAM * DSCAML1 * EMB * F11R * FAIM3 *

FCAR Fc fragment of IgA receptor (''FCAR'') is a human gene that codes for the transmembrane receptor FcαRI, also known as CD89 (Cluster of Differentiation 89). FcαRI binds the heavy-chain constant region of Immunoglobulin A (IgA) antibodies. FcαRI ...

FCER1A Fc fragment of IgE, high affinity I, receptor for; alpha polypeptide, also known as FCER1A, is a protein which in humans is encoded by the ''FCER1A'' gene. Function The high affinity IgE receptor plays a central role in allergic disease, co ...

FCGR1A High affinity immunoglobulin gamma Fc receptor I is a protein that in humans is encoded by the ''FCGR1A'' gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity... ...

* FCGR2A * FCGR2B * FCGR2C *

FCGR3A Low affinity immunoglobulin gamma Fc region receptor III-A is a protein that in humans is encoded by the ''FCGR3A'' gene. It is also known as CD16a as it is part of the cluster of differentiation The cluster of differentiation (also known as clus ...

FCGR3B FCGR3B (Fc fragment of IgG, low affinity IIIb, receptor), also known as CD16b (Cluster of Differentiation 16b), is a human gene. Clinical relevance Mutations and copy-number variations in this gene have been associated to clinical cases of glomeru ...

* FCRH1 * FCRH3 * FCRH4 *

FCRL1 Fc receptor-like protein 1 is a protein that in humans is encoded by the ''FCRL1'' gene. References Further reading * * * * * Fc receptors {{gene-1-stub ...

* FCRL2 *

FCRL3 Fc receptor-like protein 3 is a protein that in humans is encoded by the ''FCRL3'' gene. This gene encodes a member of the immunoglobulin receptor superfamily and is one of several Fc receptor-like glycoproteins clustered on the long arm of chro ...

* FCRL4 * FCRL5 * FCRL6 * FCRLA *

FGFR1 Fibroblast growth factor receptor 1 (FGFR1), also known as basic fibroblast growth factor receptor 1, fms-related tyrosine kinase-2 / Pfeiffer syndrome, and CD331, is a receptor tyrosine kinase whose ligands are specific members of the fibroblast ...

FGFR2 Fibroblast growth factor receptor 2 (FGFR2) 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. The protein ...

FGFR3 Fibroblast growth factor receptor 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 q16.3, is expressed in ...

FGFR4 Fibroblast growth factor receptor 4 is a protein that in humans is encoded by the ''FGFR4'' gene. FGFR4 has also been designated as CD334 (cluster of differentiation 334). The protein encoded by this gene is a member of the fibroblast growth fact ...

* FGFRL1 *

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 ...

FLT3 Cluster of differentiation antigen 135 (CD135) also known as fms like tyrosine kinase 3 (FLT-3), receptor-type tyrosine-protein kinase FLT3, or fetal liver kinase-2 (Flk2) is a protein that in humans is encoded by the ''FLT3'' gene. FLT3 is a cyto ...

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 * FSTL5 * GP6 * GPA33 * GPR116 *

GPR125 Adhesion G-protein coupled receptor A3 (ADGRA3), also known as GPR125, is an adhesion GPCR that in humans is encoded by the ''Adgra3'' gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the M ...

* HEPACAM *

HLA-DMA HLA class II histocompatibility antigen, DM alpha chain is a protein that in humans is encoded by the ''HLA-DMA'' gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredi ...

HLA-DMB HLA class II histocompatibility antigen, DM beta chain is a protein that in humans is encoded by the ''HLA-DMB'' gene. Function HLA-DMB belongs to the HLA class II beta chain paralogues. This class II molecule is a heterodimer consisting of a ...

* HLA-DQB *

HLA-DQB1 Major histocompatibility complex, class II, DQ beta 1, also known as HLA-DQB1, is a human gene and also denotes the genetic locus that contains this gene. The protein encoded by this gene is one of two proteins that are required to form the DQ he ...

* HMCN1 * HNT * HSPG2 * HYST2477 * ICAM3 *

ICAM5 Intercellular adhesion molecule 5 is a protein that in humans is encoded by the ''ICAM5'' gene. The protein encoded by this gene is a member of the intercellular adhesion molecule (ICAM) family. All ICAM proteins are type I transmembrane glycopr ...

* IGHA1 * IGHD * IGHE * IGSF10 * IGSF11 * IGSF2 * IGSF21 * IGSF3 * IGSF9 * IL11RA *

IL1R1 Interleukin 1 receptor, type I (IL1R1) also known as CD121a (Cluster of Differentiation 121a), is an interleukin receptor. IL1R1 also denotes its human gene. The protein encoded by this gene is a cytokine receptor that belongs to the interleukin-1 ...

* IL1R2 * IL1RAPL1 * IL1RAPL2 *

IL1RL1 Interleukin 1 receptor-like 1, also known as IL1RL1 and ST2, is a protein that in humans is encoded by the ''IL1RL1'' gene. Function IL1RL1 is a member of the Toll-like receptor superfamily based on the function of its intracellular TIR domain ...

IL1RL2 Interleukin-1 receptor-like 2 is a protein that in humans is encoded by the ''IL1RL2'' gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generati ...

* IL6R *

JAM2 Junctional adhesion molecule B is a protein that in humans is encoded by the ''JAM2'' gene. JAM2 has also been designated as CD322 (cluster of differentiation 322). Function Tight junctions represent one mode of cell-to-cell adhesion in end ...

JAM3 Junctional adhesion molecule C is a protein that in humans is encoded by the ''JAM3'' gene. Gene This gene is located on the long arm of chromosome 11 (11q25) on the Watson strand. It is 83,077 bases in length. The encoded protein is 310 amino ...

* KIR-123FM *

KIR2DL1 Killer cell immunoglobulin-like receptor 2DL1 is a protein that in humans is encoded by the ''KIR2DL1'' gene. Function Killer-cell immunoglobulin-like receptors (KIRs) are transmembrane glycoproteins expressed by natural killer cells and su ...

* KIR2DL2 * KIR2DL3 *

KIR2DL4 Killer cell immunoglobulin-like receptor 2DL4 is a protein that in humans is encoded by the ''KIR2DL4'' gene. Function Killer cell immunoglobulin-like receptors (KIRs) are transmembrane glycoproteins expressed by natural killer cells and sub ...

* KIR2DL5A * KIR2DL5B * KIR2DLX *

KIR2DS1 Killer cell immunoglobulin-like receptor, two domains, short cytoplasmic tail, 1 is a protein that in humans is encoded by the KIR2DS1 gene. Function Killer cell immunoglobulin-like receptors (KIRs) are transmembrane glycoproteins expressed ...

* KIR2DS2 * KIR2DS3 * KIR2DS4 * KIR2DS5 * KIR3DL1 *

KIR3DL2 Killer cell immunoglobulin-like receptor 3DL2 is a protein that in humans is encoded by the ''KIR3DL2'' gene. Killer cell immunoglobulin-like receptors (KIRs) are transmembrane glycoproteins expressed by natural killer cells and subsets of T ce ...

* KIR3DL3 * KIR3DS1 *

KIT Kit may refer to: Places *Kitt, Indiana, US, formerly Kit * Kit, Iran, a village in Mazandaran Province * Kit Hill, Cornwall, England People * Kit (given name), a list of people and fictional characters * Kit (surname) Animals * Young animal ...

L1CAM L1, also known as L1CAM, is a transmembrane protein member of the L1 protein family, encoded by the L1CAM gene. This protein, of 200-220 kDa, is a neuronal cell adhesion molecule with a strong implication in cell migration, adhesion, neurite outg ...

LAG3 Lymphocyte-activation gene 3, also known as LAG-3, is a protein which in humans is encoded by the ''LAG3'' gene. LAG3, which was discovered in 1990 and was designated CD223 (cluster of differentiation 223) after the Seventh Human Leucocyte Differ ...

LILRA1 Leukocyte immunoglobulin-like receptor, subfamily A (with TM domain), member 1 is a protein that in humans is encoded by the ''LILRA1'' gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the M ...

* LILRA2 *

LILRA3 Leukocyte immunoglobulin-like receptor subfamily A member 3 (LILR-A3) also known as CD85 antigen-like family member E (CD85e), immunoglobulin-like transcript 6 (ILT-6), and leukocyte immunoglobulin-like receptor 4 (LIR-4) is a protein that in hum ...

* LILRA4 * LILRA5 * LILRA6 *

LILRB1 Leukocyte immunoglobulin-like receptor subfamily B member 1 is a protein that in humans is encoded by the ''LILRB1'' gene. Function This gene is a member of the leukocyte immunoglobulin-like receptor (LIR) family, which is found in a gene clu ...

LILRB2 Leukocyte immunoglobulin-like receptor subfamily B member 2 is a protein that in humans is encoded by the ''LILRB2'' gene. This gene is a member of the leukocyte immunoglobulin-like receptor (LIR) family, which is found in a gene cluster at chr ...

* LILRB3 * LILRB4 * LILRB5 * LILRP2 * LRIG1 * LRIG2 * LRIG3 * LRIT1 * LRRC4 * LSAMP * MAG *

MALT1 Mucosa-associated lymphoid tissue lymphoma translocation protein 1 is a protein that in humans is encoded by the ''MALT1'' gene. It's the human paracaspase. Function Genetic ablation of the paracaspase gene in mice and biochemical studies have ...

* MCAM * MDGA1 * MDGA2 * MERTK * MFAP3 *

MIR ''Mir'' (russian: Мир, ; ) was a space station that operated in low Earth orbit from 1986 to 2001, operated by the Soviet Union and later by Russia. ''Mir'' was the first modular space station and was assembled in orbit from 1986 to&n ...

* MIR * MXRA5 *

MYBPC3 The myosin-binding protein C, cardiac-type is a protein that in humans is encoded by the ''MYBPC3'' gene. This isoform is expressed exclusively in heart muscle during human and mouse development, and is distinct from those expressed in slow skele ...

MYOM1 Myomesin-1 is a protein that in humans is encoded by the ''MYOM1'' gene. Myomesin-1 is expressed in muscle cells and functions to stabilize the three-dimensional conformation of the thick filament. Embryonic forms of Myomesin-1 have been detecte ...

* MYOM3 * NCA * NCAM1 * NCAM2 * NEGR1 *

NEO1 Neogenin is a protein that in humans is encoded by the ''NEO1'' gene. Interactions NEO1 has been shown to interact Advocates for Informed Choice, dba interACT or interACT Advocates for Intersex Youth, is a 501(c)(3) nonprofit organization ...

* NFASC * NOPE * NPHS1 * NPTN * NRCAM *

NRG1 Neuregulin 1, or NRG1, is a gene of the epidermal growth factor family that in humans is encoded by the ''NRG1'' gene. NRG1 is one of four proteins in the neuregulin family that act on the EGFR family of receptors. Neuregulin 1 is produced in num ...

* NT *

NTRK3 Tropomyosin receptor kinase C (TrkC), also known as NT-3 growth factor receptor, neurotrophic tyrosine kinase receptor type 3, or TrkC tyrosine kinase is a protein that in humans is encoded by the ''NTRK3'' gene. TrkC is the high affinity catalyt ...

OBSCN Obscurin is a protein that in humans is encoded by the ''OBSCN'' gene. Obscurin belongs to the family of giant sarcomeric signaling proteins that includes titin and nebulin. Obscurin is expressed in cardiac and skeletal muscle, and plays a role i ...

OBSL1 Obscurin-like protein 1 is a protein that in humans is encoded by the ''OBSL1'' gene. References Further reading * * * * * * * External links GeneReviews/NIH/NCBI/UW entry on 3-M syndrome OMIM entries on 3-M syndromePDBe-KB
provides an ...

* OPCML * PAPLN *

PDGFRA PDGFRA, i.e. platelet-derived growth factor receptor A, also termed PDGFRα, i.e. platelet-derived growth factor receptor α, or CD140a i.e. Cluster of Differentiation 140a, is a receptor located on the surface of a wide range of cell types. This re ...

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 ...

* PDGFRL * PECAM1 * PRODH2 * PSG1 * PSG10 * PSG11 * PSG11s' * PSG2 * PSG3 * PSG4 * PSG5 * PSG6 * PSG7 * PSG8 * PSG9 * PTGFRN * PTK7 * PTPRD * PTPRK *

PTPRM Receptor-type tyrosine-protein phosphatase mu is an enzyme that in humans is encoded by the ''PTPRM'' gene. Function The protein encoded by this gene is a member of the protein tyrosine phosphatase (PTP) family. Protein tyrosine phosphatases a ...

PTPRS Receptor-type tyrosine-protein phosphatase S, also known as R-PTP-S, R-PTP-sigma, or PTPσ, is an enzyme that in humans is encoded by the ''PTPRS'' gene. Function The protein encoded by this gene is a member of the protein tyrosine phosphata ...

* PTPsigma * PUNC * PVR *

PVRL1 Poliovirus receptor-related 1 (PVRL1), also known as nectin-1 and CD111 (formerly herpesvirus entry mediator C, HVEC) is a human protein of the immunoglobulin superfamily (IgSF), also considered a member of the nectins. It is a membrane protein ...

* PVRL2 * PVRL4 * RAGE *

SCN1B Sodium channel subunit beta-1 is a protein that in humans is encoded by the ''SCN1B'' gene. Voltage-gated sodium channels are essential for the generation and propagation of action potentials in striated muscle and neuronal tissues. Biochemical ...

* SDK1 * SDK2 *

SEMA3A Semaphorin-3A is a protein that in humans is encoded by the ''SEMA3A'' gene. Function The ''SEMA3A'' gene is a member of the semaphorin family and encodes a protein with an Ig-like C2-type (immunoglobulin-like) domain, a PSI domain and a Sem ...

* SEMA3B * SEMA3E *

SEMA3F Semaphorin-3F is a protein that in humans is encoded by the ''SEMA3F'' gene. The semaphorin Semaphorins are a class of secreted and membrane proteins that were originally identified as axonal growth cone guidance molecules. They primarily act ...

* SEMA3G *

SEMA4D Semaphorin-4D (SEMA4D) also known as Cluster of Differentiation 100 (CD100), is a protein of the semaphorin family that in humans is encoded by the ''SEMA4D'' gene. Function Semaphorin 4D (Sema 4D) is an axon guidance molecule which is secrete ...

* SIGLEC1 *

SIGLEC10 Sialic acid-binding Ig-like lectin 10 is a protein that in humans is encoded by the ''SIGLEC10'' gene. Siglec-G is often referred to as the murine paralog of human Siglec-10 Structure and function Like most but not all other Siglecs, Siglec- ...

* SIGLEC11 * SIGLEC12 * SIGLEC14 * SIGLEC6 * SIGLEC7 * SIGLEC8 * SIRPG *

THY1 Thy-1 or CD90 (Cluster of Differentiation 90) is a 25–37 k Da heavily N-glycosylated, glycophosphatidylinositol (GPI) anchored conserved cell surface protein with a single V-like immunoglobulin domain, originally discovered as a thymocyte anti ...

TIE1 Tyrosine kinase with immunoglobulin-like and EGF-like domains 1 also known as TIE1 is an angiopoietin receptor which in humans is encoded by the ''TIE1'' gene. Function TIE1 is a cell surface protein expressed exclusively in endothelial cells, ...

TMIGD1 Transmembrane and immunoglobulin domain containing 1 is a protein that in humans is encoded by the TMIGD1 gene. TMIGD1 was discovered by Nader Rahimi Nader Rahimi (born December 22, 1963) is a Molecular Biologist and is currently an Associat ...

TMIGD2 Transmembrane and immunoglobulin domain containing 2 is a protein that in humans is encoded by the TMIGD2 gene. TMIGD2 was discovered by Nader Rahimi Nader Rahimi (born December 22, 1963) is a Molecular Biologist and is currently an Associa ...

TTN ''ttn'' (''the total news'') was a 30 minute weekly Australian news program aimed at school-aged (9- to 14-year-old) children produced and broadcast by Network Ten from 2004 to 2008. It presented current issues and events in a way that could b ...

TYRO3 Tyrosine-protein kinase receptor TYRO3 is an enzyme that in humans is encoded by the ''TYRO3'' gene. Interactions TYRO3 has been shown to interact with: * GAS6, and * PIK3R1 Phosphatidylinositol 3-kinase regulatory subunit alpha is an enzyme ...

* UNC5D * VCAM1 * VSIG1 * VSIG2 * VSIG4 * hEMMPRIN * kir3d

References

External links

SCOP listing of immunoglobulin domains of known structure
{{Protein tertiary structure Protein domains Protein folds Single-pass transmembrane proteins

Examples

See also

References

External links