Annotations: 7KQ7

Crystal structure of IL21R in complex with an antibody Fab fragment

External Resource: Annotation

Domain Annotation: SCOP/SCOPe Classification
Domain Annotation: ECOD Classification
Domain Annotation: CATH
SAbDab Antibody Annotation
Gene Ontology: Gene Product Annotation
InterPro: Protein Family Classification
Pharos: Disease Associations

Domain Annotation: SCOP/SCOPe Classification SCOP-e Database Homepage

Chains	Domain Info	Class	Fold	Superfamily	Family	Domain	Species	Provenance Source (Version)
A [auth H]	d7kq7h_	All beta proteins	Immunoglobulin-like beta-sandwich	Immunoglobulin	V set domains (antibody variable domain-like)	automated matches	(Rattus norvegicus ) [TaxId: 10116 ],	SCOPe (2.08)
B [auth L]	d7kq7l2	All beta proteins	Immunoglobulin-like beta-sandwich	Immunoglobulin	C1 set domains (antibody constant domain-like)	automated matches	(Rattus norvegicus ) [TaxId: 10116 ],	SCOPe (2.08)
B [auth L]	d7kq7l1	All beta proteins	Immunoglobulin-like beta-sandwich	Immunoglobulin	automated matches	automated matches	(Rattus norvegicus ) [TaxId: 10116 ],	SCOPe (2.08)

Domain Annotation: ECOD Classification ECOD Database Homepage

Chains	Family Name	Domain Identifier	Architecture	Possible Homology	Homology	Topology	Family	Provenance Source (Version)
A [auth H]	Ribosomal_S24e	e7kq7H1	A: beta barrels	X: DNA methylase specificity domain	H: Bromodomain	T: Bromodomain	F: Ribosomal_S24e	ECOD (v294.2)
C [auth B]	Ribosomal_S24e	e7kq7B1	A: beta barrels	X: DNA methylase specificity domain	H: Bromodomain	T: Bromodomain	F: Ribosomal_S24e	ECOD (v294.2)
B [auth L]	Ribosomal_S24e	e7kq7L1	A: beta barrels	X: DNA methylase specificity domain	H: Bromodomain	T: Bromodomain	F: Ribosomal_S24e	ECOD (v294.2)

Domain Annotation: CATH CATH Database Homepage

Chain	Domain	Class	Architecture	Topology	Homology	Provenance Source (Version)
A [auth H]	2.60.40.10	Mainly Beta	Sandwich	Immunoglobulin-like	Immunoglobulins	CATH (utative)
B [auth L]	2.60.40.10	Mainly Beta	Sandwich	Immunoglobulin-like	Immunoglobulins	CATH (utative)

SAbDab Antibody Annotation SAbDab Database Homepage

Chain	Chain Class	Chain Subclass	Chain Type	Antigen Name(s)	Provenance Source
A [auth H]	Heavy Chain	IGHV5	-	interleukin-21 receptor	SAbDab (2026-06-12)
B [auth L]	Light Chain	IGKV3	Kappa	interleukin-21 receptor	SAbDab (2026-06-12)

Gene Ontology: Gene Product Annotation Gene Ontology Database Homepage

Chains	Polymer	Molecular Function	Biological Process	Cellular Component
A [auth H]	Antibody heavy chain	-	-	-
C [auth B]	Interleukin-21 receptor	molecular transducer activity transmembrane signaling receptor activity signaling receptor activity cytokine receptor activity immune receptor activity interleukin-21 receptor activity	cellular response to stimulus cell surface receptor signaling pathway via STAT regulation of biological process regulation of cellular process cell surface receptor signaling pathway response to stimulus signaling biological regulation cell communication cellular process signal transduction cell surface receptor signaling pathway via JAK-STAT response to cytokine cytokine-mediated signaling pathway cellular response to stimulus cell surface receptor signaling pathway via STAT regulation of biological process regulation of cellular process cell surface receptor signaling pathway response to stimulus signaling biological regulation cell communication cellular process signal transduction cell surface receptor signaling pathway via JAK-STAT response to cytokine cytokine-mediated signaling pathway response to peptide response to chemical cellular response to cytokine stimulus adaptive immune response based on somatic recombination of immune receptors built from immunoglobulin superfamily domains lymphocyte mediated immunity immune response immune system process B cell mediated immunity leukocyte mediated immunity immunoglobulin mediated immune response adaptive immune response immune effector process multicellular organismal process cell activation natural killer cell activation lymphocyte activation leukocyte activation	cell periphery cellular anatomical structure cell surface membrane plasma membrane external side of plasma membrane side of membrane
B [auth L]	Antibody light chain	-	-	-

InterPro: Protein Family Classification InterPro Database Homepage

Chains	Accession	Name	Type
C [auth B]	IPR003961	Fibronectin type III	Domain
C [auth B]	IPR003531	Short hematopoietin receptor, family 1, conserved site	Conserved Site
C [auth B]	IPR013783	Immunoglobulin-like fold	Homologous Superfamily
C [auth B]	IPR036116	Fibronectin type III superfamily	Homologous Superfamily

Pharos: Disease Associations Pharos Homepage Annotation

Chains	Drug Target	Associated Disease
C [auth B]	: Q9HBE5	cryptosporidiosis-chronic cholangitis-liver disease syndrome IgE responsiveness, atopic ulcerative colitis allergic rhinitis head and neck cancer invasive ductal breast carcinoma Lupus Erythematosus, Systemic primary biliary cholangitis systemic lupus erythematosus asthma cutaneous lupus erythematosus malignant mesothelioma psoriasis tuberculosis chronic obstructive pulmonary disease cryptosporidiosis-chronic cholangitis-liver disease syndrome IgE responsiveness, atopic ulcerative colitis allergic rhinitis head and neck cancer invasive ductal breast carcinoma Lupus Erythematosus, Systemic primary biliary cholangitis systemic lupus erythematosus asthma cutaneous lupus erythematosus malignant mesothelioma psoriasis tuberculosis chronic obstructive pulmonary disease ductal breast carcinoma in situ interstitial cystitis lung adenocarcinoma osteosarcoma Sjogren syndrome

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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.