Annotations: 6XLQ

Crystal Structure of the Human BTN3A1 Ectodomain in Complex with the CTX-2026 Fab

External Resource: Annotation

Domain Annotation: SCOP2 Classification
Domain Annotation: ECOD Classification
Domain Annotation: CATH
IMGT Antibody Annotation
SAbDab Antibody Annotation
Protein Family Annotation
Gene Ontology: Gene Product Annotation
InterPro: Protein Family Classification
Pharos: Disease Associations
Protein Modification Annotation

Domain Annotation: SCOP2 Classification SCOP2 Database Homepage

Chains	Type	Family Name	Domain Identifier	Family Identifier	Provenance Source (Version)
A	SCOP2B Superfamily	Immunoglobulin (Ig) domain-like	8081005	3000071	SCOP2B (2022-06-29)
D	SCOP2B Superfamily	Immunoglobulin (Ig) domain-like	8081005	3000071	SCOP2B (2022-06-29)
G	SCOP2B Superfamily	Immunoglobulin (Ig) domain-like	8081005	3000071	SCOP2B (2022-06-29)
J	SCOP2B Superfamily	Immunoglobulin (Ig) domain-like	8081005	3000071	SCOP2B (2022-06-29)

Domain Annotation: ECOD Classification ECOD Database Homepage

Chains	Family Name	Domain Identifier	Architecture	Possible Homology	Homology	Topology	Family	Provenance Source (Version)
A	Ldh_1_C	e6xlqA1	A: beta barrels	X: Immunoglobulin-like beta-sandwich	H: Immunoglobulin-related	T: Immunoglobulin/Fibronectin type III/E set domains/PapD-like	F: Ldh_1_C	ECOD (v294.2)
D	Ldh_1_C	e6xlqD1	A: beta barrels	X: Immunoglobulin-like beta-sandwich	H: Immunoglobulin-related	T: Immunoglobulin/Fibronectin type III/E set domains/PapD-like	F: Ldh_1_C	ECOD (v294.2)
G	Ldh_1_C	e6xlqG1	A: beta barrels	X: Immunoglobulin-like beta-sandwich	H: Immunoglobulin-related	T: Immunoglobulin/Fibronectin type III/E set domains/PapD-like	F: Ldh_1_C	ECOD (v294.2)
J	Ldh_1_C	e6xlqJ1	A: beta barrels	X: Immunoglobulin-like beta-sandwich	H: Immunoglobulin-related	T: Immunoglobulin/Fibronectin type III/E set domains/PapD-like	F: Ldh_1_C	ECOD (v294.2)
B	Ldh_1_C	e6xlqB1	A: beta barrels	X: Immunoglobulin-like beta-sandwich	H: Immunoglobulin-related	T: Immunoglobulin/Fibronectin type III/E set domains/PapD-like	F: Ldh_1_C	ECOD (v294.2)
E	Ldh_1_C	e6xlqE1	A: beta barrels	X: Immunoglobulin-like beta-sandwich	H: Immunoglobulin-related	T: Immunoglobulin/Fibronectin type III/E set domains/PapD-like	F: Ldh_1_C	ECOD (v294.2)
H	Ldh_1_C	e6xlqH1	A: beta barrels	X: Immunoglobulin-like beta-sandwich	H: Immunoglobulin-related	T: Immunoglobulin/Fibronectin type III/E set domains/PapD-like	F: Ldh_1_C	ECOD (v294.2)
K	Ldh_1_C	e6xlqK1	A: beta barrels	X: Immunoglobulin-like beta-sandwich	H: Immunoglobulin-related	T: Immunoglobulin/Fibronectin type III/E set domains/PapD-like	F: Ldh_1_C	ECOD (v294.2)
C	Ldh_1_C	e6xlqC1	A: beta barrels	X: Immunoglobulin-like beta-sandwich	H: Immunoglobulin-related	T: Immunoglobulin/Fibronectin type III/E set domains/PapD-like	F: Ldh_1_C	ECOD (v294.2)
F	Ldh_1_C	e6xlqF1	A: beta barrels	X: Immunoglobulin-like beta-sandwich	H: Immunoglobulin-related	T: Immunoglobulin/Fibronectin type III/E set domains/PapD-like	F: Ldh_1_C	ECOD (v294.2)
I	Ldh_1_C	e6xlqI1	A: beta barrels	X: Immunoglobulin-like beta-sandwich	H: Immunoglobulin-related	T: Immunoglobulin/Fibronectin type III/E set domains/PapD-like	F: Ldh_1_C	ECOD (v294.2)
L	Ldh_1_C	e6xlqL1	A: beta barrels	X: Immunoglobulin-like beta-sandwich	H: Immunoglobulin-related	T: Immunoglobulin/Fibronectin type III/E set domains/PapD-like	F: Ldh_1_C	ECOD (v294.2)

Domain Annotation: CATH CATH Database Homepage

Chain	Domain	Class	Architecture	Topology	Homology	Provenance Source (Version)
C	2.60.40.10	Mainly Beta	Sandwich	Immunoglobulin-like	Immunoglobulins	CATH (utative)
F	2.60.40.10	Mainly Beta	Sandwich	Immunoglobulin-like	Immunoglobulins	CATH (utative)
I	2.60.40.10	Mainly Beta	Sandwich	Immunoglobulin-like	Immunoglobulins	CATH (utative)
L	2.60.40.10	Mainly Beta	Sandwich	Immunoglobulin-like	Immunoglobulins	CATH (utative)

IMGT Antibody Annotation IMGT Database Homepage

Chain	Protein Name	Description	Organism Name	Gene Allele Name(s)	Domain Name(s)	Receptor Type	Receptor Description	Provenance Source
B, E, H, K	Fab CTX-2026	VH-CH1	Homo sapiens (human)	IGHV1-202, IGHJ601, IGHG101, IGHG102, IGHG104, IGHG105, IGHG112, IGHG114, IGHG113, IGHG109, IGHG110, IGHG107, IGHG1*11	V-DOMAIN VH, C-DOMAIN CH1	IG	FAB-GAMMA-1_KAPPA	IMGT (202618-0)
C, F, I, L	Fab CTX-2026	L-KAPPA	Homo sapiens (human)	IGKV1-1201, IGKV1D-1201, IGKV1-1202, IGKV1D-1202, IGKJ401, IGKJ402, IGKC*01	V-DOMAIN V-KAPPA, C-DOMAIN C-KAPPA	IG	FAB-GAMMA-1_KAPPA	IMGT (202618-0)

SAbDab Antibody Annotation SAbDab Database Homepage

Chain	Chain Class	Chain Subclass	Chain Type	Antigen Name(s)	Provenance Source
B, E, H, K	Heavy Chain	IGHV1	-	butyrophilin subfamily 3 member a1	SAbDab (2026-05-15)
C, F, I, L	Light Chain	IGKV1	Kappa	butyrophilin subfamily 3 member a1	SAbDab (2026-05-15)

Protein Family Annotation Pfam Database Homepage

Chains	Accession	Name	Description	Comments	Source
A, D, G, J	PF07686	Immunoglobulin V-set domain (V-set)	Immunoglobulin V-set domain	This domain is found in antibodies as well as neural protein P0 and CTL4 amongst others.	Domain
A, D, G, J	PF22705	Butyrophilin subfamily 3 member A2-like, Ig-C domain (C2-set_3)	Butyrophilin subfamily 3 member A2-like, Ig-C domain	This domain is found in human Butyrophilin subfamily 3 member A2 (BTN3A2), a protein that plays a role in T-cell responses in the adaptive immune response. BTN3A2 shows two extracellular domains: an N-terminal Ig-V like domain (Pfam:PF07686) and a C- ...	This domain is found in human Butyrophilin subfamily 3 member A2 (BTN3A2), a protein that plays a role in T-cell responses in the adaptive immune response. BTN3A2 shows two extracellular domains: an N-terminal Ig-V like domain (Pfam:PF07686) and a C-terminal Ig-C type domain that is located in the centre of the protein sequence [6].	Domain

Gene Ontology: Gene Product Annotation Gene Ontology Database Homepage

Chains	Polymer	Molecular Function	Biological Process	Cellular Component
A, D, G, J	Butyrophilin subfamily 3 member A1	protein binding binding signaling receptor binding	cellular response to stimulus immune response-regulating cell surface receptor signaling pathway regulation of cellular process response to stimulus signaling positive regulation of biological process cell communication positive regulation of response to stimulus immune response-activating signaling pathway immune response-regulating signaling pathway positive regulation of immune response regulation of immune system process signal transduction positive regulation of immune system process cellular response to stimulus immune response-regulating cell surface receptor signaling pathway regulation of cellular process response to stimulus signaling positive regulation of biological process cell communication positive regulation of response to stimulus immune response-activating signaling pathway immune response-regulating signaling pathway positive regulation of immune response regulation of immune system process signal transduction positive regulation of immune system process regulation of biological process cell surface receptor signaling pathway immune response-activating cell surface receptor signaling pathway immune response biological regulation T cell receptor signaling pathway regulation of response to stimulus immune system process regulation of immune response cellular process antigen receptor-mediated signaling pathway activation of immune response adaptive immune response multicellular organismal process positive regulation of macromolecule biosynthetic process positive regulation of metabolic process positive regulation of biosynthetic process cytokine production regulation of cytokine production positive regulation of macromolecule metabolic process regulation of multicellular organismal process positive regulation of cellular process regulation of biosynthetic process regulation of macromolecule metabolic process gene expression macromolecule biosynthetic process regulation of gene expression biosynthetic process positive regulation of gene expression positive regulation of multicellular organismal process regulation of macromolecule biosynthetic process metabolic process macromolecule metabolic process positive regulation of cytokine production regulation of metabolic process cell population proliferation cell activation lymphocyte activation leukocyte proliferation activated T cell proliferation leukocyte activation mononuclear cell proliferation T cell activation lymphocyte proliferation T cell proliferation regulation of type II interferon production type II interferon production positive regulation of type II interferon production	cell periphery cellular anatomical structure cell surface membrane plasma membrane external side of plasma membrane side of membrane
B, E, H, K	CTX-2026 Heavy Chain	-	-	-
C, F, I, L	CTX-2026 Light Chain	-	-	-

InterPro: Protein Family Classification InterPro Database Homepage

Chains	Accession	Name	Type
A, D, G, J	IPR036179	Immunoglobulin-like domain superfamily	Homologous Superfamily
A, D, G, J	IPR001870	B30.2/SPRY domain	Domain
A, D, G, J	IPR006574	SPRY-associated	Domain
A, D, G, J	IPR050504	BTN/MOG-like	Family
A, D, G, J	IPR003879	Butyrophylin-like, SPRY domain	Domain
A, D, G, J	IPR013320	Concanavalin A-like lectin/glucanase domain superfamily	Homologous Superfamily
A, D, G, J	IPR053896	Butyrophilin subfamily 3 member A2-like, Ig-C domain	Domain
A, D, G, J	IPR013783	Immunoglobulin-like fold	Homologous Superfamily
A, D, G, J	IPR013106	Immunoglobulin V-set domain	Domain
A, D, G, J	IPR003599	Immunoglobulin domain subtype	Domain
A, D, G, J	IPR043136	B30.2/SPRY domain superfamily	Homologous Superfamily
A, D, G, J	IPR007110	Immunoglobulin-like domain	Domain
A, D, G, J	IPR037954	Butyrophilin subfamily 3, PRY/SPRY domain	Domain
A, D, G, J	IPR003877	SPRY domain	Domain

Pharos: Disease Associations Pharos Homepage Annotation

Chains	Drug Target	Associated Disease
A, D, G, J	: O00481	lung carcinoma postmenopausal osteoporosis squamous cell lung carcinoma attention deficit hyperactivity disorder, inattentive type bone Paget disease cutaneous lupus erythematosus gastroesophageal reflux disease Hypogonadal Osteoporosis in Males ovarian cancer ulcerative colitis autism spectrum disorder chronic obstructive pulmonary disease dental caries lung cancer osteoporosis lung carcinoma postmenopausal osteoporosis squamous cell lung carcinoma attention deficit hyperactivity disorder, inattentive type bone Paget disease cutaneous lupus erythematosus gastroesophageal reflux disease Hypogonadal Osteoporosis in Males ovarian cancer ulcerative colitis autism spectrum disorder chronic obstructive pulmonary disease dental caries lung cancer osteoporosis pilocytic astrocytoma Sjogren syndrome Crohn disease endogenous depression osteosarcoma

Protein Modification Annotation

Modified Residue(s)
Chain	Residue(s)	Description
B, E, H, K	PCA	Parent Component: GLN : AA0031 : 2-pyrrolidone-5-carboxylic acid (Gln) MOD:00040 , 2-pyrrolidone-5-carboxylic acid (Glu) MOD:00420

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RCSB PDB Core Operations are funded by the U.S. National Science Foundation (DBI-2321666), the US Department of Energy (DE-SC0019749), and the National Cancer Institute, National Institute of Allergy and Infectious Diseases, and National Institute of General Medical Sciences of the National Institutes of Health under grant R01GM157729. RCSB PDB uses resources of the National Energy Research Scientific Computing Center (NERSC), a Department of Energy User Facility.