3IU3 | pdb_00003iu3

Crystal structure of the Fab fragment of therapeutic antibody Basiliximab in complex with IL-2Ra (CD25) ectodomain

External Resource: Annotation

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

Domain Annotation: SCOP2 Classification SCOP2 Database Homepage

Chains	Type	Family Name	Domain Identifier	Family Identifier	Provenance Source (Version)
I [auth K]	SCOP2B Superfamily	Sushi/CCP/SCR domain	8037668	3000902	SCOP2B (2022-06-29)
I [auth K]	SCOP2B Superfamily	Sushi/CCP/SCR domain	8037669	3000902	SCOP2B (2022-06-29)
H [auth J]	SCOP2B Superfamily	Sushi/CCP/SCR domain	8037669	3000902	SCOP2B (2022-06-29)
H [auth J]	SCOP2B Superfamily	Sushi/CCP/SCR domain	8037668	3000902	SCOP2B (2022-06-29)
G [auth I]	SCOP2B Superfamily	Sushi/CCP/SCR domain	8037668	3000902	SCOP2B (2022-06-29)
G [auth I]	SCOP2B Superfamily	Sushi/CCP/SCR domain	8037669	3000902	SCOP2B (2022-06-29)
F [auth L]	SCOP2B Superfamily	Immunoglobulin (Ig) domain-like	8091527	3000071	SCOP2B (2022-06-29)
D	SCOP2B Superfamily	Immunoglobulin (Ig) domain-like	8091527	3000071	SCOP2B (2022-06-29)
B	SCOP2B Superfamily	Immunoglobulin (Ig) domain-like	8091527	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)
I [auth K]	Trypsin	e3iu3K1	A: a/b three-layered sandwiches	X: cradle loop barrel	H: RIFT-related	T: acid protease	F: Trypsin	ECOD (v294.1)
H [auth J]	Trypsin	e3iu3J1	A: a/b three-layered sandwiches	X: cradle loop barrel	H: RIFT-related	T: acid protease	F: Trypsin	ECOD (v294.1)
G [auth I]	ALO	e3iu3I3	A: a/b three-layered sandwiches	X: DEATH domain	H: Ten stranded beta/alpha barrel	T: Ten stranded beta/alpha barrel	F: ALO	ECOD (v294.1)
F [auth L]	Trypsin	e3iu3L1	A: a/b three-layered sandwiches	X: cradle loop barrel	H: RIFT-related	T: acid protease	F: Trypsin	ECOD (v294.1)
D	Trypsin	e3iu3D1	A: a/b three-layered sandwiches	X: cradle loop barrel	H: RIFT-related	T: acid protease	F: Trypsin	ECOD (v294.1)
B	Trypsin	e3iu3B1	A: a/b three-layered sandwiches	X: cradle loop barrel	H: RIFT-related	T: acid protease	F: Trypsin	ECOD (v294.1)
E [auth H]	Trypsin	e3iu3H1	A: a/b three-layered sandwiches	X: cradle loop barrel	H: RIFT-related	T: acid protease	F: Trypsin	ECOD (v294.1)
C	Trypsin	e3iu3C1	A: a/b three-layered sandwiches	X: cradle loop barrel	H: RIFT-related	T: acid protease	F: Trypsin	ECOD (v294.1)
A	SUFU	e3iu3A1	A: a/b three-layered sandwiches	X: EGF-like	H: EGF-related	T: EGF/Laminin	F: SUFU	ECOD (v294.1)

Domain Annotation: CATH CATH Database Homepage

Chain	Domain	Class	Architecture	Topology	Homology	Provenance Source (Version)
I [auth K]	2.10.70.10	Mainly Beta	Ribbon	Complement Module	domain 1	CATH (4.3.0)
I [auth K]	2.20.28.230	Mainly Beta	Single Sheet	Rubrerythrin, domain 2		CATH (4.3.0)
H [auth J]	2.10.70.10	Mainly Beta	Ribbon	Complement Module	domain 1	CATH (4.3.0)
H [auth J]	2.20.28.230	Mainly Beta	Single Sheet	Rubrerythrin, domain 2		CATH (4.3.0)
G [auth I]	2.10.70.10	Mainly Beta	Ribbon	Complement Module	domain 1	CATH (4.3.0)
G [auth I]	2.20.28.230	Mainly Beta	Single Sheet	Rubrerythrin, domain 2		CATH (4.3.0)
F [auth L]	2.60.40.10	Mainly Beta	Sandwich	Immunoglobulin-like	Immunoglobulins	CATH (4.3.0)
D	2.60.40.10	Mainly Beta	Sandwich	Immunoglobulin-like	Immunoglobulins	CATH (4.3.0)
B	2.60.40.10	Mainly Beta	Sandwich	Immunoglobulin-like	Immunoglobulins	CATH (4.3.0)
E [auth H]	2.60.40.10	Mainly Beta	Sandwich	Immunoglobulin-like	Immunoglobulins	CATH (4.3.0)
C	2.60.40.10	Mainly Beta	Sandwich	Immunoglobulin-like	Immunoglobulins	CATH (4.3.0)
A	2.60.40.10	Mainly Beta	Sandwich	Immunoglobulin-like	Immunoglobulins	CATH (4.3.0)

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, D, F [auth L]	basiliximab	L-KAPPA	Chimeric (chimeric)	IGKV4-7001, IGKJ101, IGKJ102, IGKJ201, IGKC*01	V-DOMAIN V-KAPPA, C-DOMAIN C-KAPPA	IG	FAB-GAMMA-1_KAPPA	IMGT (202611-0)
A, C, E [auth H]	basiliximab	VH-CH1	Chimeric (chimeric)	IGHV1-501, IGHJ201, IGHG1*03	V-DOMAIN VH, C-DOMAIN CH1	IG	FAB-GAMMA-1_KAPPA	IMGT (202611-0)

SAbDab Antibody Annotation SAbDab Database Homepage

Chain	Chain Class	Chain Subclass	Chain Type	Antigen Name(s)	Provenance Source
B, D, F [auth L]	Light Chain	IGKV4	Kappa	interleukin-2 receptor alpha chain	SAbDab (2026-03-27)
A, C, E [auth H]	Heavy Chain	IGHV1	-	interleukin-2 receptor alpha chain	SAbDab (2026-03-27)

Thera-SAbDab Antibody Annotation Thera-SAbDab Database Homepage

Chain	Name	Target	Provenance Source
B, D, F [auth L]	Basiliximab	IL2RA/CD25	Therapeutic SAbDab (2026-03-27)
A, C, E [auth H]	Basiliximab	IL2RA/CD25	Therapeutic SAbDab (2026-03-27)

Protein Family Annotation Pfam Database Homepage

Chains	Accession	Name	Description	Comments	Source
G [auth I], H [auth J], I [auth K]	PF00084	Sushi repeat (SCR repeat) (Sushi)	Sushi repeat (SCR repeat)		Domain
B, D, F [auth L]	PF07654	Immunoglobulin C1-set domain (C1-set)	Immunoglobulin C1-set domain		Domain

Gene Ontology: Gene Product Annotation Gene Ontology Database Homepage

Chains	Polymer	Molecular Function	Biological Process	Cellular Component
G [auth I], H [auth J], I [auth K]	Interleukin-2 receptor alpha chain	protein binding binding growth factor binding cytokine binding interleukin-2 binding molecular transducer activity interleukin-2 receptor activity transmembrane signaling receptor activity signaling receptor activity cytokine receptor activity immune receptor activity	multicellular organismal process regulation of cellular process positive regulation of cell population proliferation regulation of leukocyte activation regulation of cell activation positive regulation of cell activation T cell activation lymphocyte proliferation positive regulation of leukocyte activation regulation of immune system process positive regulation of immune system process regulation of leukocyte proliferation regulation of biological process cell population proliferation multicellular organismal process regulation of cellular process positive regulation of cell population proliferation regulation of leukocyte activation regulation of cell activation positive regulation of cell activation T cell activation lymphocyte proliferation positive regulation of leukocyte activation regulation of immune system process positive regulation of immune system process regulation of leukocyte proliferation regulation of biological process cell population proliferation positive regulation of T cell activation positive regulation of lymphocyte proliferation positive regulation of T cell proliferation positive regulation of activated T cell proliferation regulation of cell population proliferation mononuclear cell proliferation regulation of leukocyte cell-cell adhesion positive regulation of leukocyte proliferation positive regulation of multicellular organismal process regulation of activated T cell proliferation positive regulation of biological process positive regulation of leukocyte cell-cell adhesion lymphocyte activation leukocyte proliferation leukocyte cell-cell adhesion leukocyte activation activated T cell proliferation positive regulation of cell-cell adhesion positive regulation of lymphocyte activation cell adhesion cell-cell adhesion positive regulation of mononuclear cell proliferation regulation of multicellular organismal process regulation of cell-cell adhesion positive regulation of cellular process T cell proliferation regulation of lymphocyte proliferation positive regulation of cell adhesion regulation of cell adhesion biological regulation cell activation regulation of T cell activation regulation of T cell proliferation immune system process regulation of mononuclear cell proliferation cellular process regulation of lymphocyte activation regulation of alpha-beta T cell activation regulation of alpha-beta T cell proliferation alpha-beta T cell proliferation CD4-positive, alpha-beta T cell activation alpha-beta T cell activation CD4-positive, alpha-beta T cell proliferation regulation of CD4-positive, alpha-beta T cell proliferation regulation of CD4-positive, alpha-beta T cell activation cellular response to stimulus cell surface receptor signaling pathway response to stimulus signaling signal transduction cell communication defense response immune response response to stress inflammatory response inflammatory response to antigenic stimulus interleukin-2-mediated signaling pathway cellular response to interleukin-2 response to cytokine cytokine-mediated signaling pathway response to peptide response to interleukin-2 response to chemical cellular response to cytokine stimulus homeostatic process T cell homeostatic proliferation T cell homeostasis multicellular organismal-level homeostasis regulation of T cell homeostatic proliferation leukocyte homeostasis homeostasis of number of cells lymphocyte homeostasis apoptotic process cell death programmed cell death regulation of defense response regulation of response to external stimulus negative regulation of inflammatory response negative regulation of response to stimulus negative regulation of biological process response to external stimulus regulation of inflammatory response regulation of response to stimulus negative regulation of response to external stimulus regulation of response to stress negative regulation of defense response immune system development developmental process T cell tolerance induction multicellular organism development anatomical structure development regulation of tolerance induction regulation of T cell tolerance induction tolerance induction system development negative regulation of lymphocyte proliferation negative regulation of T cell proliferation negative regulation of cell adhesion negative regulation of leukocyte proliferation negative regulation of T cell activation negative regulation of leukocyte cell-cell adhesion negative regulation of cell-cell adhesion negative regulation of multicellular organismal process negative regulation of leukocyte activation negative regulation of lymphocyte activation negative regulation of mononuclear cell proliferation negative regulation of cellular process negative regulation of cell population proliferation negative regulation of cell activation negative regulation of immune system process Notch signaling pathway leukocyte apoptotic process lymphocyte apoptotic process activation-induced cell death of T cells T cell apoptotic process regulation of leukocyte differentiation mononuclear cell differentiation regulation of cell differentiation lymphocyte differentiation positive regulation of T cell differentiation regulation of cell development positive regulation of developmental process cell differentiation T cell differentiation positive regulation of cell development leukocyte differentiation cellular developmental process regulation of developmental process cell development regulation of T cell differentiation positive regulation of hemopoiesis positive regulation of cell differentiation regulation of lymphocyte differentiation regulation of multicellular organismal development hemopoiesis regulation of hemopoiesis positive regulation of leukocyte differentiation positive regulation of lymphocyte differentiation	cell periphery cellular anatomical structure cell surface membrane plasma membrane external side of plasma membrane side of membrane protein-containing complex plasma membrane protein complex plasma membrane signaling receptor complex membrane protein complex interleukin-2 receptor complex receptor complex
B, D, F [auth L]	Light chain of Fab fragment of Basiliximab	binding antigen binding	adaptive immune response based on somatic recombination of immune receptors built from immunoglobulin superfamily domains lymphocyte mediated immunity response to stimulus immune response immune system process B cell mediated immunity leukocyte mediated immunity immunoglobulin mediated immune response adaptive immune response immune effector process cellular response to stimulus immune response-regulating cell surface receptor signaling pathway regulation of cellular process signaling adaptive immune response based on somatic recombination of immune receptors built from immunoglobulin superfamily domains lymphocyte mediated immunity response to stimulus immune response immune system process B cell mediated immunity leukocyte mediated immunity immunoglobulin mediated immune response adaptive immune response immune effector process cellular response to stimulus immune response-regulating cell surface receptor signaling pathway regulation of cellular process 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 B cell receptor signaling pathway biological regulation regulation of response to stimulus regulation of immune response cellular process antigen receptor-mediated signaling pathway activation of immune response	protein-containing complex IgA immunoglobulin complex immunoglobulin complex cellular anatomical structure extracellular region extracellular space blood microparticle IgM immunoglobulin complex IgE immunoglobulin complex IgD immunoglobulin complex extracellular exosome membrane-bounded organelle extracellular vesicle extracellular organelle protein-containing complex IgA immunoglobulin complex immunoglobulin complex cellular anatomical structure extracellular region extracellular space blood microparticle IgM immunoglobulin complex IgE immunoglobulin complex IgD immunoglobulin complex extracellular exosome membrane-bounded organelle extracellular vesicle extracellular organelle organelle vesicle extracellular membrane-bounded organelle cell periphery plasma membrane membrane IgG immunoglobulin complex
A, C, E [auth H]	Heavy chain of Fab fragment of Basiliximab	-	-	-

InterPro: Protein Family Classification InterPro Database Homepage

Chains	Accession	Name	Type
G [auth I], H [auth J], I [auth K]	IPR015486	Interleukin-2 receptor alpha	Family
G [auth I], H [auth J], I [auth K]	IPR000436	Sushi/SCR/CCP domain	Domain
G [auth I], H [auth J], I [auth K]	IPR035976	Sushi/SCR/CCP superfamily	Homologous Superfamily
B, D, F [auth L]	IPR036179	Immunoglobulin-like domain superfamily	Homologous Superfamily
B, D, F [auth L]	IPR050380	Immune Recognition and Response Modulators	Family
B, D, F [auth L]	IPR003597	Immunoglobulin C1-set	Domain
B, D, F [auth L]	IPR013783	Immunoglobulin-like fold	Homologous Superfamily
B, D, F [auth L]	IPR007110	Immunoglobulin-like domain	Domain
B, D, F [auth L]	IPR003006	Immunoglobulin/major histocompatibility complex, conserved site	Conserved Site

Pharos: Disease Associations Pharos Homepage Annotation

Chains	Drug Target	Associated Disease
G [auth I], H [auth J], I [auth K]	Pharos: P01589	rheumatoid arthritis immunodeficiency due to CD25 deficiency Crohn disease alopecia areata HIV infectious disease juvenile idiopathic arthritis type 1 diabetes mellitus glomerulonephritis type 1 diabetes mellitus 10 multiple sclerosis oligoarticular juvenile idiopathic arthritis malignant mesothelioma chronic beryllium disease schizophrenia allergic contact dermatitis rheumatoid arthritis immunodeficiency due to CD25 deficiency Crohn disease alopecia areata HIV infectious disease juvenile idiopathic arthritis type 1 diabetes mellitus glomerulonephritis type 1 diabetes mellitus 10 multiple sclerosis oligoarticular juvenile idiopathic arthritis malignant mesothelioma chronic beryllium disease schizophrenia allergic contact dermatitis Regional enteritis sclerosing cholangitis Graves disease acquired metabolic disease allergic rhinitis major depressive disorder atopic eczema psoriasis relapsing-remitting multiple sclerosis rheumatoid factor-negative juvenile idiopathic arthritis glioblastoma Hashimoto thyroiditis vitiligo hypothyroidism acute myeloid leukemia inflammatory bowel disease large cell medulloblastoma atypical teratoid rhabdoid tumor neuroblastoma ovarian cancer Crohn's colitis diabetes mellitus ileocolitis interstitial cystitis lung adenocarcinoma asthma marginal zone lymphoma autoimmune disease non-small cell lung carcinoma common variable immunodeficiency primary cutaneous T-cell lymphoma
B, D, F [auth L]	Pharos: P01834	recurrent infections associated with rare immunoglobulin isotypes deficiency myositis dysgammaglobulinemia Hepatomegaly acquired idiopathic inflammatory myopathy selective IgG immunodeficiency

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.