3iu3

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

Method: X-RAY DIFFRACTION

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1. Protein Identity and Related Structures Protein Identity & Related Structures

Interleukin-2 receptor alpha chain

Homo sapiens

State in the Current Structure

Assembly	Physical composition	Protein state	Molecular copy count	Associated components	Data consistency
1	Other combination	Heteromer	Protein 3 其他Polymer 1	Heavy chain of Fab fragment of Basiliximab × 1 Light chain of Fab fragment of Basiliximab × 1 beta-D-mannopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose × 1	Consistent with protein count
2	Other combination	Heteromer	Protein 3 其他Polymer 1	Heavy chain of Fab fragment of Basiliximab × 1 Light chain of Fab fragment of Basiliximab × 1 beta-D-mannopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose × 1	Consistent with protein count
3	Other combination	Heteromer	Protein 3 其他Polymer 1	Heavy chain of Fab fragment of Basiliximab × 1 Light chain of Fab fragment of Basiliximab × 1 beta-D-mannopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose × 1	Consistent with protein count

Other States of the Same Protein in the Database

View Construct and Data Evidence

UniProt name	IL2RA_HUMAN
Isoform	—
PDB entities	3
Chains and sequence ranges	Author chain I； PDBConstruct 1–217； UniProt 22–238 Author chain J； PDBConstruct 1–217； UniProt 22–238 Author chain K； PDBConstruct 1–217； UniProt 22–238

The page prioritizes protein identity, the current assembly, associated components, oligomeric state and cross-PDB links. Chain mapping and sequence ranges are retained as data evidence. Internal IDs, import timestamps and assembly operation expressions are maintenance fields and are not shown here.

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2. Structure Basics 2. Structure Basics

Entry ID entry_id	3iu3
Deposition date deposition_date	2009-08-29
Structure title title	Crystal structure of the Fab fragment of therapeutic antibody Basiliximab in complex with IL-2Ra (CD25) ectodomain
Keywords keywords	;IL-2Ra, CD25, Basiliximab, Simulect, therapeutic antibody, Disulfide bond, Glycoprotein, Membrane, Receptor, Sushi, Transmembrane, IMMUNE SYSTEM ;; IMMUNE SYSTEM
Experimental Method method	X-RAY DIFFRACTION

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3. Official assembly/model SAXS Official SAXS Profiles

This page reads only the latest assembly calculations. Every curve maps to an explicit PDB entry, official biological assembly and coordinate model.

3iu3__assembly_3__model_1

Assembly 3 · Model 1 · CRYSOL 4.1.3-1-20251215 (887e7ef)

Download this curve (.dat)

3iu3__assembly_3__model_1 | I(q)

100 plotted points; both axes use logarithmic scales.

3iu3__assembly_3__model_1 | P(r) · Pending

P(r) will be calculated and displayed separately for the same assembly/model.

Rg（Guinier）	29.57 Å
Rg (electron density)	29.27 Å
Total Rg	29.87 Å
Atom count	4214
Residues	542
Excluded volume	74236 Å³
Maximum q	0.500 Å⁻¹

Assembly	Model	Structure unit	Oligomeric description	Status	CRYSOL	Actions
1	1	`3iu3__assembly_1__model_1`	trimeric （3）	Success	4.1.3-1-20251215 (887e7ef)	View Download
2	1	`3iu3__assembly_2__model_1`	trimeric （3）	Success	4.1.3-1-20251215 (887e7ef)	View Download
3	1	`3iu3__assembly_3__model_1`	trimeric （3）	Success	4.1.3-1-20251215 (887e7ef)	View Download

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4. Crystallography and Experiment 4. Crystallography & Experiment

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5. Entities and Polymers Entities & Polymers (4)

Entity 1 Entity 1 polymer

Description description	Heavy chain of Fab fragment of Basiliximab
Molecular weight formula_weight	23144.8 kDa
Source method src_method	man
Copy count entity_count	3

Polymer Polymer

Polymer type type	polypeptide(L)
Chain IDs strand_id	A,C,H
Atom count atom_count	12566

QLQQSGTVLARPGASVKMSCKASGYSFTRYWMHWIKQRPGQGLEWIGAIYPGNSDTSYNQKFEGKAKLTAVTSASTAYMELSSLTHEDSAVYYCSRDYGYYFDFWGQGTTLTVSSASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDKRVEP

Source Source

Source organism organism	Mus musculus, Homo sapiens
Common name common_name	mouse, human
Host organism host_organism	Escherichia coli

Entity 2 Entity 2 polymer

Description description	Light chain of Fab fragment of Basiliximab
Molecular weight formula_weight	22882.3 kDa
Source method src_method	man
Copy count entity_count	3

Polymer Polymer

Polymer type type	polypeptide(L)
Chain IDs strand_id	B,D,L

QIVSTQSPAIMSASPGEKVTMTCSASSSRSYMQWYQQKPGTSPKRWIYDTSKLASGVPARFSGSGSGTSYSLTISSMEAEDAATYYCHQRSSYTFGGGTKLEIKRTVAAPSVFIFPPSDEQLKSGTASVVCLLNNFYPREAKVQWKVDNALQSGNSQESVTEQDSKDSTYSLSSTLTLSKADYEKHKVYACEVTHQGLSSPVTKSFNRGE

Source Source

Source organism organism	Mus musculus, Homo sapiens
Common name common_name	mouse, human
Host organism host_organism	Escherichia coli

Entity 3 Entity 3 polymer

Description description	Interleukin-2 receptor alpha chain
Molecular weight formula_weight	25388.3 kDa
Source method src_method	man
Copy count entity_count	3

Polymer Polymer

Polymer type type	polypeptide(L)
Chain IDs strand_id	I,J,K

ELCDDDPPEIPHATFKAMAYKEGTMLNCECKRGFRRIKSGSLYMLCTGNSSHSSWDNQCQCTSSATRNTTKQVTPQPEEQKERKTTEMQSPMQPVDQASLPGHCREPPPWENEATERIYHFVVGQMVYYQCVQGYRALHRGPAESVCKMTHGKTRWTQPQLICTGEMETSQFPGEEKPQASPEGRPESETSCLVTTTDFQIQTEMAATMETSIFTTEHHHHHH

Source Source

Source organism organism	Homo sapiens
Common name common_name	human
NCBI taxonomy ID ncbi_taxonomy_id	9606
Host organism host_organism	Spodoptera frugiperda

Entity 4 Entity 4 branched

Description description	beta-D-mannopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose
Molecular weight formula_weight	586.5 kDa
Source method src_method	man
Copy count entity_count	3

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6. Fold Classification (SCOP + CATH) 18 domains

CATH v4.4 (18 domains)

Domain ID domain_id	3iu3A01
Class class	2 — Mainly Beta
Architecture architecture	60 — Sandwich
Topology topology	40 — Immunoglobulin-like
Homologous superfamily homologous superfamily	10 — Immunoglobulins

Domain ID domain_id	3iu3A02
Class class	2 — Mainly Beta
Architecture architecture	60 — Sandwich
Topology topology	40 — Immunoglobulin-like
Homologous superfamily homologous superfamily	10 — Immunoglobulins

Domain ID domain_id	3iu3B01
Class class	2 — Mainly Beta
Architecture architecture	60 — Sandwich
Topology topology	40 — Immunoglobulin-like
Homologous superfamily homologous superfamily	10 — Immunoglobulins

Domain ID domain_id	3iu3B02
Class class	2 — Mainly Beta
Architecture architecture	60 — Sandwich
Topology topology	40 — Immunoglobulin-like
Homologous superfamily homologous superfamily	10 — Immunoglobulins

Domain ID domain_id	3iu3C01
Class class	2 — Mainly Beta
Architecture architecture	60 — Sandwich
Topology topology	40 — Immunoglobulin-like
Homologous superfamily homologous superfamily	10 — Immunoglobulins

Domain ID domain_id	3iu3C02
Class class	2 — Mainly Beta
Architecture architecture	60 — Sandwich
Topology topology	40 — Immunoglobulin-like
Homologous superfamily homologous superfamily	10 — Immunoglobulins

Domain ID domain_id	3iu3D01
Class class	2 — Mainly Beta
Architecture architecture	60 — Sandwich
Topology topology	40 — Immunoglobulin-like
Homologous superfamily homologous superfamily	10 — Immunoglobulins

Domain ID domain_id	3iu3D02
Class class	2 — Mainly Beta
Architecture architecture	60 — Sandwich
Topology topology	40 — Immunoglobulin-like
Homologous superfamily homologous superfamily	10 — Immunoglobulins

Domain ID domain_id	3iu3H01
Class class	2 — Mainly Beta
Architecture architecture	60 — Sandwich
Topology topology	40 — Immunoglobulin-like
Homologous superfamily homologous superfamily	10 — Immunoglobulins

Domain ID domain_id	3iu3H02
Class class	2 — Mainly Beta
Architecture architecture	60 — Sandwich
Topology topology	40 — Immunoglobulin-like
Homologous superfamily homologous superfamily	10 — Immunoglobulins

Domain ID domain_id	3iu3I01
Class class	2 — Mainly Beta
Architecture architecture	10 — Ribbon
Topology topology	70 — Complement Module; domain 1
Homologous superfamily homologous superfamily	10 — Complement Module, domain 1

Domain ID domain_id	3iu3I02
Class class	2 — Mainly Beta
Architecture architecture	20 — Single Sheet
Topology topology	28 — Rubrerythrin, domain 2
Homologous superfamily homologous superfamily	230 —

Domain ID domain_id	3iu3J01
Class class	2 — Mainly Beta
Architecture architecture	10 — Ribbon
Topology topology	70 — Complement Module; domain 1
Homologous superfamily homologous superfamily	10 — Complement Module, domain 1

Domain ID domain_id	3iu3J02
Class class	2 — Mainly Beta
Architecture architecture	20 — Single Sheet
Topology topology	28 — Rubrerythrin, domain 2
Homologous superfamily homologous superfamily	230 —

Domain ID domain_id	3iu3K01
Class class	2 — Mainly Beta
Architecture architecture	10 — Ribbon
Topology topology	70 — Complement Module; domain 1
Homologous superfamily homologous superfamily	10 — Complement Module, domain 1

Domain ID domain_id	3iu3K02
Class class	2 — Mainly Beta
Architecture architecture	20 — Single Sheet
Topology topology	28 — Rubrerythrin, domain 2
Homologous superfamily homologous superfamily	230 —

Domain ID domain_id	3iu3L01
Class class	2 — Mainly Beta
Architecture architecture	60 — Sandwich
Topology topology	40 — Immunoglobulin-like
Homologous superfamily homologous superfamily	10 — Immunoglobulins

Domain ID domain_id	3iu3L02
Class class	2 — Mainly Beta
Architecture architecture	60 — Sandwich
Topology topology	40 — Immunoglobulin-like
Homologous superfamily homologous superfamily	10 — Immunoglobulins

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Unit-cell length a length_a	137.051 Å
Unit-cell length b length_b	137.051 Å
Unit-cell length c length_c	459.095 Å
Unit-cell angle α angle_alpha	90.00 °
Unit-cell angle β angle_beta	90.00 °
Unit-cell angle γ angle_gamma	120.00 °
Molecules per unit cell Z z_pdb	36

Space group space_group	P 65 2 2
Space-group number int_tables_number	179
Crystal system crystal_system	—

Resolution resolution	2.900 Å
Low-resolution limit resolution_low	47.381 Å
R factor r_factor	0.2172
R_work r_work	0.2148
R_free r_free	0.2620

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

1. Protein Identity and Related Structures Protein Identity & Related Structures

Interleukin-2 receptor alpha chain

State in the Current Structure

Other States of the Same Protein in the Database

2. Structure Basics 2. Structure Basics

3. Official assembly/model SAXS Official SAXS Profiles

3iu3__assembly_3__model_1

3iu3__assembly_3__model_1 | I(q)

3iu3__assembly_3__model_1 | P(r) · Pending

4. Crystallography and Experiment 4. Crystallography & Experiment

Unit cell Unit Cell

Symmetry Symmetry

Refinement Refinement

Diffraction experiment Diffraction

5. Entities and Polymers Entities & Polymers (4)

Entity 1 Entity 1 polymer

Polymer Polymer

Source Source

Entity 2 Entity 2 polymer

Polymer Polymer

Source Source

Entity 3 Entity 3 polymer

Polymer Polymer

Source Source

Entity 4 Entity 4 branched

6. Fold Classification (SCOP + CATH) 18 domains

CATH v4.4 (18 domains)

7. Citations (1)

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

1. Protein Identity and Related Structures Protein Identity & Related Structures

Interleukin-2 receptor alpha chain

State in the Current Structure

Other States of the Same Protein in the Database

Monomer

Homodimer

Homotetramer

Other homooligomers

Heteromeric or nucleic-acid complex

2. Structure Basics 2. Structure Basics

3. Official assembly/model SAXS Official SAXS Profiles

3iu3__assembly_3__model_1

3iu3__assembly_3__model_1 | I(q)

3iu3__assembly_3__model_1 | P(r) · Pending

4. Crystallography and Experiment 4. Crystallography & Experiment

Unit cell Unit Cell

Symmetry Symmetry

Refinement Refinement

Diffraction experiment Diffraction

5. Entities and Polymers Entities & Polymers (4)

Entity 1 Entity 1 polymer

Polymer Polymer

Source Source

Entity 2 Entity 2 polymer

Polymer Polymer

Source Source

Entity 3 Entity 3 polymer

Polymer Polymer

Source Source

Entity 4 Entity 4 branched

6. Fold Classification (SCOP + CATH) 18 domains

CATH v4.4 (18 domains)

7. Citations (1)