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Conserved domains on  [gi|91105174|ref|NP_001761|]
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B-lymphocyte antigen CD19 isoform 2 precursor [Homo sapiens]

Protein Classification

Graphical summary

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List of domain hits

 Name Accession Description Interval E-value
CD19_protodomain_1_2 cd23999
CD19 (Cluster of Differentiation 19), a unique double immunoglobulin (Ig)-fold protodomain 1 ...
 24-115 2.23e-51

CD19 (Cluster of Differentiation 19), a unique double immunoglobulin (Ig)-fold protodomain 1 and 2; CD19, also known as B-Lymphocyte Surface Antigen B4, T-Cell Surface Antigen Leu-12, and CVID3, is a transmembrane receptor present on various types of B cells, including progenitor, naive, and memory B cells, as well as plasmablasts. Until recently, it was believed to comprise two extracellular immunoglobulin (Ig) structural domains arranged in tandem with C2 topology. However, recent crystal structures have shown that the CD19 extracellular domain contains a unique double Ig domain that is responsible for its binding to proteins such as CD21, CD81, and CD225, which regulate B cell activation and survival. A recent analysis of the CD19 extracellular domain sequence reveals two "Ig domains", but the structure demonstrates that these two domains are not folded independently and connected in tandem. Rather, they fold together as one intertwined domain that can be referred to as a "double Ig" domain. Each of the two regular Ig domain sequences has a noticeably short linker that forms a loop between strands C' and D, rather than allowing the formation of a C" strand. Additionally, the two Ig-domain sequences are separated by a long linker that is structured as a small insertion domain, enabling both Ig sequences to fold together as a unique double Ig-domain. The CD19 domain comprises four "protodomains": two formed by A'B-CC' strands and two by DE-FG strands that interdigitate to form a novel double Ig fold. When analyzing this double Ig domain in terms of the usual Ig-fold, A'B-CC' protodomain of the first Ig sequence combines with DE-FG protodomain of the second, and vice versa. Hence, the second combined Ig fold is inverted, with DE-FG protodomain of the first Ig sequence combining with A'B-CC' protodomain of the second Ig sequence and in that order, as if it were a circular permutation, obtained only through structural folding. This group contains the protodomains 1 and 2 of the CD19 double Ig domain.


:

Pssm-ID: 467826  Cd Length: 92  Bit Score: 170.68  E-value: 2.23e-51
                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 91105174  24 LVVKVEEGDNAVLQCLKGTSDGPTQQLTWSRESPLKPFLKLSLGLPGLGIHMRPLAIWLFIFNVSQQMGGFYLCQPGPPS 103
Cdd:cd23999   1 LLVEVEEGDNAVLPCLIGPSDGPPEQLTWSRGGQLEPFLQLSLGSPGLGAQVGPLGIWLFIFNVSEQMGGFYLCELGPPS 80

                        90
                ....*....|..
gi 91105174 104 EKAWQPGWTVNV 115
Cdd:cd23999  81 KQAWQPGWTVSV 92
CD19_protodomain_3_4 cd23998
CD19 (Cluster of Differentiation 19), a unique double immunoglobulin (Ig)-fold protodomain 3 ...
 186-274 9.65e-47

CD19 (Cluster of Differentiation 19), a unique double immunoglobulin (Ig)-fold protodomain 3 and 4; CD19, also known as B-Lymphocyte Surface Antigen B4, T-Cell Surface Antigen Leu-12, and CVID3, is a transmembrane receptor present on various types of B cells, including progenitor, naive, and memory B cells, as well as plasmablasts. Until recently, it was believed to comprise two extracellular immunoglobulin (Ig) structural domains arranged in tandem with C2 topology. However, recent crystal structures have shown that the CD19 extracellular domain contains a unique double Ig domain that is responsible for its binding to proteins such as CD21, CD81, and CD225, which regulate B cell activation and survival. A recent analysis of the CD19 extracellular domain sequence reveals two "Ig domains", but the structure demonstrates that these two domains are not folded independently and connected in tandem. Rather, they fold together as one intertwined domain that can be referred to as a "double Ig" domain. Each of the two regular Ig domain sequences has a noticeably short linker that forms a loop between strands C' and D, rather than allowing the formation of a C" strand. Additionally, the two Ig-domain sequences are separated by a long linker that is structured as a small insertion domain, enabling both Ig sequences to fold together as a unique double Ig-domain. The CD19 domain comprises four "protodomains": two formed by A'B-CC' strands and two by DE-FG strands that interdigitate to form a novel double Ig fold. When analyzing this double Ig domain in terms of the usual Ig-fold, A'B-CC' protodomain of the first Ig sequence combines with DE-FG protodomain of the second, and vice versa. Hence, the second combined Ig fold is inverted, with DE-FG protodomain of the first Ig sequence combining with A'B-CC' protodomain of the second Ig sequence and in that order, as if it were a circular permutation, obtained only through structural folding. This group contains the protodomains 3 and 4 of the CD19 double Ig domain.


:

Pssm-ID: 467825  Cd Length: 95  Bit Score: 158.42  E-value: 9.65e-47
                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 91105174 186 QDLTMAPGSTLWLSCGVPPDSVSRGPLSWTHVHPK-GPKSLLSLELKDDRPARDMWVM-----ETGLLLPRATAQDAGKY 259
Cdd:cd23998   1 QDLTVAPGSTLWLSCGVPPDSGTRGPISWTHVHPKpSNTSLLSLELKEDRPAREKWVLgtlrgGALLLLPRATAQDAGIY 80

                        90
                ....*....|....*
gi 91105174 260 YCHRGNLTMSFHLEI 274
Cdd:cd23998  81 HCHLGNRTISMELTV 95
 
Name Accession Description Interval E-value
CD19_protodomain_1_2 cd23999
CD19 (Cluster of Differentiation 19), a unique double immunoglobulin (Ig)-fold protodomain 1 ...
 24-115 2.23e-51

CD19 (Cluster of Differentiation 19), a unique double immunoglobulin (Ig)-fold protodomain 1 and 2; CD19, also known as B-Lymphocyte Surface Antigen B4, T-Cell Surface Antigen Leu-12, and CVID3, is a transmembrane receptor present on various types of B cells, including progenitor, naive, and memory B cells, as well as plasmablasts. Until recently, it was believed to comprise two extracellular immunoglobulin (Ig) structural domains arranged in tandem with C2 topology. However, recent crystal structures have shown that the CD19 extracellular domain contains a unique double Ig domain that is responsible for its binding to proteins such as CD21, CD81, and CD225, which regulate B cell activation and survival. A recent analysis of the CD19 extracellular domain sequence reveals two "Ig domains", but the structure demonstrates that these two domains are not folded independently and connected in tandem. Rather, they fold together as one intertwined domain that can be referred to as a "double Ig" domain. Each of the two regular Ig domain sequences has a noticeably short linker that forms a loop between strands C' and D, rather than allowing the formation of a C" strand. Additionally, the two Ig-domain sequences are separated by a long linker that is structured as a small insertion domain, enabling both Ig sequences to fold together as a unique double Ig-domain. The CD19 domain comprises four "protodomains": two formed by A'B-CC' strands and two by DE-FG strands that interdigitate to form a novel double Ig fold. When analyzing this double Ig domain in terms of the usual Ig-fold, A'B-CC' protodomain of the first Ig sequence combines with DE-FG protodomain of the second, and vice versa. Hence, the second combined Ig fold is inverted, with DE-FG protodomain of the first Ig sequence combining with A'B-CC' protodomain of the second Ig sequence and in that order, as if it were a circular permutation, obtained only through structural folding. This group contains the protodomains 1 and 2 of the CD19 double Ig domain.


Pssm-ID: 467826  Cd Length: 92  Bit Score: 170.68  E-value: 2.23e-51
                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 91105174  24 LVVKVEEGDNAVLQCLKGTSDGPTQQLTWSRESPLKPFLKLSLGLPGLGIHMRPLAIWLFIFNVSQQMGGFYLCQPGPPS 103
Cdd:cd23999   1 LLVEVEEGDNAVLPCLIGPSDGPPEQLTWSRGGQLEPFLQLSLGSPGLGAQVGPLGIWLFIFNVSEQMGGFYLCELGPPS 80

                        90
                ....*....|..
gi 91105174 104 EKAWQPGWTVNV 115
Cdd:cd23999  81 KQAWQPGWTVSV 92
CD19_protodomain_3_4 cd23998
CD19 (Cluster of Differentiation 19), a unique double immunoglobulin (Ig)-fold protodomain 3 ...
 186-274 9.65e-47

CD19 (Cluster of Differentiation 19), a unique double immunoglobulin (Ig)-fold protodomain 3 and 4; CD19, also known as B-Lymphocyte Surface Antigen B4, T-Cell Surface Antigen Leu-12, and CVID3, is a transmembrane receptor present on various types of B cells, including progenitor, naive, and memory B cells, as well as plasmablasts. Until recently, it was believed to comprise two extracellular immunoglobulin (Ig) structural domains arranged in tandem with C2 topology. However, recent crystal structures have shown that the CD19 extracellular domain contains a unique double Ig domain that is responsible for its binding to proteins such as CD21, CD81, and CD225, which regulate B cell activation and survival. A recent analysis of the CD19 extracellular domain sequence reveals two "Ig domains", but the structure demonstrates that these two domains are not folded independently and connected in tandem. Rather, they fold together as one intertwined domain that can be referred to as a "double Ig" domain. Each of the two regular Ig domain sequences has a noticeably short linker that forms a loop between strands C' and D, rather than allowing the formation of a C" strand. Additionally, the two Ig-domain sequences are separated by a long linker that is structured as a small insertion domain, enabling both Ig sequences to fold together as a unique double Ig-domain. The CD19 domain comprises four "protodomains": two formed by A'B-CC' strands and two by DE-FG strands that interdigitate to form a novel double Ig fold. When analyzing this double Ig domain in terms of the usual Ig-fold, A'B-CC' protodomain of the first Ig sequence combines with DE-FG protodomain of the second, and vice versa. Hence, the second combined Ig fold is inverted, with DE-FG protodomain of the first Ig sequence combining with A'B-CC' protodomain of the second Ig sequence and in that order, as if it were a circular permutation, obtained only through structural folding. This group contains the protodomains 3 and 4 of the CD19 double Ig domain.


Pssm-ID: 467825  Cd Length: 95  Bit Score: 158.42  E-value: 9.65e-47
                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 91105174 186 QDLTMAPGSTLWLSCGVPPDSVSRGPLSWTHVHPK-GPKSLLSLELKDDRPARDMWVM-----ETGLLLPRATAQDAGKY 259
Cdd:cd23998   1 QDLTVAPGSTLWLSCGVPPDSGTRGPISWTHVHPKpSNTSLLSLELKEDRPAREKWVLgtlrgGALLLLPRATAQDAGIY 80

                        90
                ....*....|....*
gi 91105174 260 YCHRGNLTMSFHLEI 274
Cdd:cd23998  81 HCHLGNRTISMELTV 95
IG_like smart00410
Immunoglobulin like; IG domains that cannot be classified into one of IGv1, IGc1, IGc2, IG.
 23-115 4.83e-06

Immunoglobulin like; IG domains that cannot be classified into one of IGv1, IGc1, IGc2, IG.


Pssm-ID: 214653 [Multi-domain]  Cd Length: 85  Bit Score: 44.80  E-value: 4.83e-06
                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 91105174     23 PLVVKVEEGDNAVLQCLkgTSDGPTQQLTWSRESPLKPFLKlslglPGLGIHMRPLAIWLFIFNVSQQMGGFYLCQPGPP 102
Cdd:smart00410   1 PPSVTVKEGESVTLSCE--ASGSPPPEVTWYKQGGKLLAES-----GRFSVSRSGSTSTLTISNVTPEDSGTYTCAATNS 73

                           90
                   ....*....|...
gi 91105174    103 SEKAWQpGWTVNV 115
Cdd:smart00410  74 SGSASS-GTTLTV 85
IG_like smart00410
Immunoglobulin like; IG domains that cannot be classified into one of IGv1, IGc1, IGc2, IG.
 185-274 1.88e-04

Immunoglobulin like; IG domains that cannot be classified into one of IGv1, IGc1, IGc2, IG.


Pssm-ID: 214653 [Multi-domain]  Cd Length: 85  Bit Score: 40.18  E-value: 1.88e-04
                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 91105174    185 SQDLTMAPGSTLWLSCGVPPDSVSRgpLSWTHvhpKGPKSLLSlelkddrPARDMWVMETG---LLLPRATAQDAGKYYC 261
Cdd:smart00410   1 PPSVTVKEGESVTLSCEASGSPPPE--VTWYK---QGGKLLAE-------SGRFSVSRSGStstLTISNVTPEDSGTYTC 68

                           90
                   ....*....|....*..
gi 91105174    262 HR----GNLTMSFHLEI 274
Cdd:smart00410  69 AAtnssGSASSGTTLTV 85
Ig_3 pfam13927
Immunoglobulin domain; This family contains immunoglobulin-like domains.
 22-98 4.23e-03

Immunoglobulin domain; This family contains immunoglobulin-like domains.


Pssm-ID: 464046 [Multi-domain]  Cd Length: 78  Bit Score: 36.39  E-value: 4.23e-03
                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 91105174    22 EPLVVKVEEGDNAVLQCLkgTSDGPTQQLTWSRESPLKPFLKLSLGLPGLGIHMrplaiwLFIFNVSQQMGGFYLCQ 98
Cdd:pfam13927   7 SPSSVTVREGETVTLTCE--ATGSPPPTITWYKNGEPISSGSTRSRSLSGSNST------LTISNVTRSDAGTYTCV 75
 
Name Accession Description Interval E-value
CD19_protodomain_1_2 cd23999
CD19 (Cluster of Differentiation 19), a unique double immunoglobulin (Ig)-fold protodomain 1 ...
 24-115 2.23e-51

CD19 (Cluster of Differentiation 19), a unique double immunoglobulin (Ig)-fold protodomain 1 and 2; CD19, also known as B-Lymphocyte Surface Antigen B4, T-Cell Surface Antigen Leu-12, and CVID3, is a transmembrane receptor present on various types of B cells, including progenitor, naive, and memory B cells, as well as plasmablasts. Until recently, it was believed to comprise two extracellular immunoglobulin (Ig) structural domains arranged in tandem with C2 topology. However, recent crystal structures have shown that the CD19 extracellular domain contains a unique double Ig domain that is responsible for its binding to proteins such as CD21, CD81, and CD225, which regulate B cell activation and survival. A recent analysis of the CD19 extracellular domain sequence reveals two "Ig domains", but the structure demonstrates that these two domains are not folded independently and connected in tandem. Rather, they fold together as one intertwined domain that can be referred to as a "double Ig" domain. Each of the two regular Ig domain sequences has a noticeably short linker that forms a loop between strands C' and D, rather than allowing the formation of a C" strand. Additionally, the two Ig-domain sequences are separated by a long linker that is structured as a small insertion domain, enabling both Ig sequences to fold together as a unique double Ig-domain. The CD19 domain comprises four "protodomains": two formed by A'B-CC' strands and two by DE-FG strands that interdigitate to form a novel double Ig fold. When analyzing this double Ig domain in terms of the usual Ig-fold, A'B-CC' protodomain of the first Ig sequence combines with DE-FG protodomain of the second, and vice versa. Hence, the second combined Ig fold is inverted, with DE-FG protodomain of the first Ig sequence combining with A'B-CC' protodomain of the second Ig sequence and in that order, as if it were a circular permutation, obtained only through structural folding. This group contains the protodomains 1 and 2 of the CD19 double Ig domain.


Pssm-ID: 467826  Cd Length: 92  Bit Score: 170.68  E-value: 2.23e-51
                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 91105174  24 LVVKVEEGDNAVLQCLKGTSDGPTQQLTWSRESPLKPFLKLSLGLPGLGIHMRPLAIWLFIFNVSQQMGGFYLCQPGPPS 103
Cdd:cd23999   1 LLVEVEEGDNAVLPCLIGPSDGPPEQLTWSRGGQLEPFLQLSLGSPGLGAQVGPLGIWLFIFNVSEQMGGFYLCELGPPS 80

                        90
                ....*....|..
gi 91105174 104 EKAWQPGWTVNV 115
Cdd:cd23999  81 KQAWQPGWTVSV 92
CD19_protodomain_3_4 cd23998
CD19 (Cluster of Differentiation 19), a unique double immunoglobulin (Ig)-fold protodomain 3 ...
 186-274 9.65e-47

CD19 (Cluster of Differentiation 19), a unique double immunoglobulin (Ig)-fold protodomain 3 and 4; CD19, also known as B-Lymphocyte Surface Antigen B4, T-Cell Surface Antigen Leu-12, and CVID3, is a transmembrane receptor present on various types of B cells, including progenitor, naive, and memory B cells, as well as plasmablasts. Until recently, it was believed to comprise two extracellular immunoglobulin (Ig) structural domains arranged in tandem with C2 topology. However, recent crystal structures have shown that the CD19 extracellular domain contains a unique double Ig domain that is responsible for its binding to proteins such as CD21, CD81, and CD225, which regulate B cell activation and survival. A recent analysis of the CD19 extracellular domain sequence reveals two "Ig domains", but the structure demonstrates that these two domains are not folded independently and connected in tandem. Rather, they fold together as one intertwined domain that can be referred to as a "double Ig" domain. Each of the two regular Ig domain sequences has a noticeably short linker that forms a loop between strands C' and D, rather than allowing the formation of a C" strand. Additionally, the two Ig-domain sequences are separated by a long linker that is structured as a small insertion domain, enabling both Ig sequences to fold together as a unique double Ig-domain. The CD19 domain comprises four "protodomains": two formed by A'B-CC' strands and two by DE-FG strands that interdigitate to form a novel double Ig fold. When analyzing this double Ig domain in terms of the usual Ig-fold, A'B-CC' protodomain of the first Ig sequence combines with DE-FG protodomain of the second, and vice versa. Hence, the second combined Ig fold is inverted, with DE-FG protodomain of the first Ig sequence combining with A'B-CC' protodomain of the second Ig sequence and in that order, as if it were a circular permutation, obtained only through structural folding. This group contains the protodomains 3 and 4 of the CD19 double Ig domain.


Pssm-ID: 467825  Cd Length: 95  Bit Score: 158.42  E-value: 9.65e-47
                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 91105174 186 QDLTMAPGSTLWLSCGVPPDSVSRGPLSWTHVHPK-GPKSLLSLELKDDRPARDMWVM-----ETGLLLPRATAQDAGKY 259
Cdd:cd23998   1 QDLTVAPGSTLWLSCGVPPDSGTRGPISWTHVHPKpSNTSLLSLELKEDRPAREKWVLgtlrgGALLLLPRATAQDAGIY 80

                        90
                ....*....|....*
gi 91105174 260 YCHRGNLTMSFHLEI 274
Cdd:cd23998  81 HCHLGNRTISMELTV 95
CD19_double_Ig cd23997
CD19 (Cluster of Differentiation 19), a unique double immunoglobulin (Ig)-fold domain; CD19, ...
 24-115 3.28e-36

CD19 (Cluster of Differentiation 19), a unique double immunoglobulin (Ig)-fold domain; CD19, also known as B-Lymphocyte Surface Antigen B4, T-Cell Surface Antigen Leu-12, and CVID3, is a transmembrane receptor present on various types of B cells, including progenitor, naive, and memory B cells, as well as plasmablasts. Until recently, it was believed to comprise two extracellular immunoglobulin (Ig) structural domains arranged in tandem with C2 topology. However, recent crystal structures have shown that the CD19 extracellular domain contains a unique double Ig domain that is responsible for its binding to proteins such as CD21, CD81, and CD225, which regulate B cell activation and survival. A recent analysis of the CD19 extracellular domain sequence reveals two "Ig domains", but the structure demonstrates that these two domains are not folded independently and connected in tandem. Rather, they fold together as one intertwined domain that can be referred to as a "double Ig" domain. Each of the two regular Ig domain sequences has a noticeably short linker that forms a loop between strands C' and D, rather than allowing the formation of a C" strand. Additionally, the two Ig-domain sequences are separated by a long linker that is structured as a small insertion domain, enabling both Ig sequences to fold together as a unique double Ig-domain. The CD19 domain comprises four "protodomains": two formed by A'B-CC' strands and two by DE-FG strands that interdigitate to form a novel double Ig fold. When analyzing this double Ig domain in terms of the usual Ig-fold, A'B-CC' protodomain of the first Ig sequence combines with DE-FG protodomain of the second, and vice versa. Hence, the second combined Ig fold is inverted, with DE-FG protodomain of the first Ig sequence combining with A'B-CC' protodomain of the second Ig sequence and in that order, as if it were a circular permutation, obtained only through structural folding.


Pssm-ID: 467824  Cd Length: 89  Bit Score: 129.76  E-value: 3.28e-36
                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 91105174  24 LVVKVEEGDNAVLQCLKGTSDGPTQQLTWSRESPLKPFLKLSLGLPGLGIHMRPLAIWLFIFNVSQQMGGFYLCQPGPPS 103
Cdd:cd23997   1 LDVTVAEGSTLWLPCLVPPSDGPRGPLTWSRGHPKTPLLSLELGSPGLWVLVGPLGILLLLPNVSAQMGGFYLCELGNLS 80

                        90
                ....*....|..
gi 91105174 104 ekaWQPGWTVNV 115
Cdd:cd23997  81 ---WTIGWTVSV 89
Ig_Semaphorin_C cd04979
Immunoglobulin (Ig)-like domain at the C-terminus of semaphorins; The members here are ...
 182-286 1.02e-26

Immunoglobulin (Ig)-like domain at the C-terminus of semaphorins; The members here are composed of the immunoglobulin (Ig)-like domain in semaphorins. Semaphorins are transmembrane protein that have important roles in a variety of tissues. Functionally, semaphorins were initially characterized for their importance in the development of the nervous system and in axonal guidance. Later they have been found to be important for the formation and functioning of the cardiovascular, endocrine, gastrointestinal, hepatic, immune, musculoskeletal, renal, reproductive, and respiratory systems. Semaphorins function through binding to their receptors and transmembrane semaphorins also serves as receptors themselves. Although molecular mechanism of semaphorins is poorly understood, the Ig-like domains may be involved in ligand binding or dimerization.


Pssm-ID: 409368  Cd Length: 88  Bit Score: 103.69  E-value: 1.02e-26
                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 91105174 182 QSLSQDLTMaPGSTLWLSCGVPPdsvSRGPLSWTHVHPKGPKSllslelkddRPARDMWVMETGLLLPRATAQDAGKYYC 261
Cdd:cd04979   1 TSFKQISVK-EGDTVILSCSVKS---NNAPVTWIHNGKKVPRY---------RSPRLVLKTERGLLIRSAQEADAGVYEC 67

                        90       100
                ....*....|....*....|....*
gi 91105174 262 HRGNLTmsfhLEITARPVLWHWLLR 286
Cdd:cd04979  68 HSGERV----LGSTLRSVTLHVLER 88
CD19_double_Ig cd23997
CD19 (Cluster of Differentiation 19), a unique double immunoglobulin (Ig)-fold domain; CD19, ...
 186-274 5.46e-26

CD19 (Cluster of Differentiation 19), a unique double immunoglobulin (Ig)-fold domain; CD19, also known as B-Lymphocyte Surface Antigen B4, T-Cell Surface Antigen Leu-12, and CVID3, is a transmembrane receptor present on various types of B cells, including progenitor, naive, and memory B cells, as well as plasmablasts. Until recently, it was believed to comprise two extracellular immunoglobulin (Ig) structural domains arranged in tandem with C2 topology. However, recent crystal structures have shown that the CD19 extracellular domain contains a unique double Ig domain that is responsible for its binding to proteins such as CD21, CD81, and CD225, which regulate B cell activation and survival. A recent analysis of the CD19 extracellular domain sequence reveals two "Ig domains", but the structure demonstrates that these two domains are not folded independently and connected in tandem. Rather, they fold together as one intertwined domain that can be referred to as a "double Ig" domain. Each of the two regular Ig domain sequences has a noticeably short linker that forms a loop between strands C' and D, rather than allowing the formation of a C" strand. Additionally, the two Ig-domain sequences are separated by a long linker that is structured as a small insertion domain, enabling both Ig sequences to fold together as a unique double Ig-domain. The CD19 domain comprises four "protodomains": two formed by A'B-CC' strands and two by DE-FG strands that interdigitate to form a novel double Ig fold. When analyzing this double Ig domain in terms of the usual Ig-fold, A'B-CC' protodomain of the first Ig sequence combines with DE-FG protodomain of the second, and vice versa. Hence, the second combined Ig fold is inverted, with DE-FG protodomain of the first Ig sequence combining with A'B-CC' protodomain of the second Ig sequence and in that order, as if it were a circular permutation, obtained only through structural folding.


Pssm-ID: 467824  Cd Length: 89  Bit Score: 101.64  E-value: 5.46e-26
                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 91105174 186 QDLTMAPGSTLWLSCGVPPDSVSRGPLSWTHVHPKgpKSLLSLELKDdrpaRDMWVMET----GLLLPRATAQDAGKYYC 261
Cdd:cd23997   1 LDVTVAEGSTLWLPCLVPPSDGPRGPLTWSRGHPK--TPLLSLELGS----PGLWVLVGplgiLLLLPNVSAQMGGFYLC 74

                        90
                ....*....|....*
gi 91105174 262 HRGNL--TMSFHLEI 274
Cdd:cd23997  75 ELGNLswTIGWTVSV 89
IG_like smart00410
Immunoglobulin like; IG domains that cannot be classified into one of IGv1, IGc1, IGc2, IG.
 23-115 4.83e-06

Immunoglobulin like; IG domains that cannot be classified into one of IGv1, IGc1, IGc2, IG.


Pssm-ID: 214653 [Multi-domain]  Cd Length: 85  Bit Score: 44.80  E-value: 4.83e-06
                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 91105174     23 PLVVKVEEGDNAVLQCLkgTSDGPTQQLTWSRESPLKPFLKlslglPGLGIHMRPLAIWLFIFNVSQQMGGFYLCQPGPP 102
Cdd:smart00410   1 PPSVTVKEGESVTLSCE--ASGSPPPEVTWYKQGGKLLAES-----GRFSVSRSGSTSTLTISNVTPEDSGTYTCAATNS 73

                           90
                   ....*....|...
gi 91105174    103 SEKAWQpGWTVNV 115
Cdd:smart00410  74 SGSASS-GTTLTV 85
IG_like smart00410
Immunoglobulin like; IG domains that cannot be classified into one of IGv1, IGc1, IGc2, IG.
 185-274 1.88e-04

Immunoglobulin like; IG domains that cannot be classified into one of IGv1, IGc1, IGc2, IG.


Pssm-ID: 214653 [Multi-domain]  Cd Length: 85  Bit Score: 40.18  E-value: 1.88e-04
                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 91105174    185 SQDLTMAPGSTLWLSCGVPPDSVSRgpLSWTHvhpKGPKSLLSlelkddrPARDMWVMETG---LLLPRATAQDAGKYYC 261
Cdd:smart00410   1 PPSVTVKEGESVTLSCEASGSPPPE--VTWYK---QGGKLLAE-------SGRFSVSRSGStstLTISNVTPEDSGTYTC 68

                           90
                   ....*....|....*..
gi 91105174    262 HR----GNLTMSFHLEI 274
Cdd:smart00410  69 AAtnssGSASSGTTLTV 85
Ig_3 pfam13927
Immunoglobulin domain; This family contains immunoglobulin-like domains.
 22-98 4.23e-03

Immunoglobulin domain; This family contains immunoglobulin-like domains.


Pssm-ID: 464046 [Multi-domain]  Cd Length: 78  Bit Score: 36.39  E-value: 4.23e-03
                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 91105174    22 EPLVVKVEEGDNAVLQCLkgTSDGPTQQLTWSRESPLKPFLKLSLGLPGLGIHMrplaiwLFIFNVSQQMGGFYLCQ 98
Cdd:pfam13927   7 SPSSVTVREGETVTLTCE--ATGSPPPTITWYKNGEPISSGSTRSRSLSGSNST------LTISNVTRSDAGTYTCV 75
V-set pfam07686
Immunoglobulin V-set domain; This domain is found in antibodies as well as neural protein P0 ...
 21-115 6.57e-03

Immunoglobulin V-set domain; This domain is found in antibodies as well as neural protein P0 and CTL4 amongst others.


Pssm-ID: 462230  Cd Length: 109  Bit Score: 36.67  E-value: 6.57e-03
                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 91105174    21 EEPLVVKVEEGDNAVLQC-LKGTSDGPTQQLTWSRESPLK-PFLKLSLGLPGLGIHMRPLAI-W----------LFIFNV 87
Cdd:pfam07686   1 QTPREVTVALGGSVTLPCtYSSSMSEASTSVYWYRQPPGKgPTFLIAYYSNGSEEGVKKGRFsGrgdpsngdgsLTIQNL 80

                          90       100
                  ....*....|....*....|....*...
gi 91105174    88 SQQMGGFYLCQPGPPSEKAWQPGWTVNV 115
Cdd:pfam07686  81 TLSDSGTYTCAVIPSGEGVFGKGTRLTV 108
Ig_Semaphorin_C cd04979
Immunoglobulin (Ig)-like domain at the C-terminus of semaphorins; The members here are ...
 20-100 9.81e-03

Immunoglobulin (Ig)-like domain at the C-terminus of semaphorins; The members here are composed of the immunoglobulin (Ig)-like domain in semaphorins. Semaphorins are transmembrane protein that have important roles in a variety of tissues. Functionally, semaphorins were initially characterized for their importance in the development of the nervous system and in axonal guidance. Later they have been found to be important for the formation and functioning of the cardiovascular, endocrine, gastrointestinal, hepatic, immune, musculoskeletal, renal, reproductive, and respiratory systems. Semaphorins function through binding to their receptors and transmembrane semaphorins also serves as receptors themselves. Although molecular mechanism of semaphorins is poorly understood, the Ig-like domains may be involved in ligand binding or dimerization.


Pssm-ID: 409368  Cd Length: 88  Bit Score: 35.51  E-value: 9.81e-03
                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 91105174  20 PEEPLVVKveEGDNAVLQCLKGTSDGPtqqLTWSRESPLKPflklSLGLPGLGIHMRPLaiwLFIFNVSQQMGGFYLCQP 99
Cdd:cd04979   2 SFKQISVK--EGDTVILSCSVKSNNAP---VTWIHNGKKVP----RYRSPRLVLKTERG---LLIRSAQEADAGVYECHS 69


                .
gi 91105174 100 G 100
Cdd:cd04979  70 G 70
 
Blast search parameters
Data Source: Precalculated data, version = cdd.v.3.21
Preset Options:Database: CDSEARCH/cdd   Low complexity filter: no  Composition Based Adjustment: yes   E-value threshold: 0.01

References:

  • Wang J et al. (2023), "The conserved domain database in 2023", Nucleic Acids Res.51(D)384-8.
  • Lu S et al. (2020), "The conserved domain database in 2020", Nucleic Acids Res.48(D)265-8.
  • Marchler-Bauer A et al. (2017), "CDD/SPARCLE: functional classification of proteins via subfamily domain architectures.", Nucleic Acids Res.45(D)200-3.
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