SAXSdb — 7b2m

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

Complement C4 beta chain

OrganismNot specified

State in the Current Structure

Assembly	Physical composition	Protein state	Molecular copy count	Associated components	Data consistency
1	Protein heterocomplex	Heteromer	Protein 4	Anti-C4b nanobody E3 × 1 2-acetamido-2-deoxy-beta-D-glucopyranose × 4	Consistent with protein count

Other States of the Same Protein in the Database

View Construct and Data Evidence

UniProt name	CO4A_HUMAN
Isoform	—
PDB entities	1, 2, 3
Chains and sequence ranges	Author chain A； PDBConstruct 1–656； UniProt 20–675 Author chain B； PDBConstruct 1–767； UniProt 680–1446 Author chain C； PDBConstruct 1–291； UniProt 1454–1744

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	7b2m
Deposition date deposition_date	2020-11-27
Structure title title	Cryo-EM structure of complement C4b in complex with nanobody E3
Keywords keywords	Complement, nanobody, C4b, complement classical pathway, nanobody-antigen complex, IMMUNE SYSTEM; IMMUNE SYSTEM
Experimental Method method	ELECTRON MICROSCOPY

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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.

7b2m__assembly_1__model_1

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

Download this curve (.dat)

7b2m__assembly_1__model_1 | I(q)

100 plotted points; both axes use logarithmic scales.

7b2m__assembly_1__model_1 | P(r) · Pending

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

Rg（Guinier）	44.70 Å
Rg (electron density)	44.64 Å
Total Rg	44.80 Å
Atom count	23250
Residues	1506
Excluded volume	207590 Å³
Maximum q	0.500 Å⁻¹

Assembly	Model	Structure unit	Oligomeric description	Status	CRYSOL	Actions
1	1	`7b2m__assembly_1__model_1`	tetrameric （4）	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 (5)

Entity 1 Entity 1 polymer

Description description	Complement C4 beta chain
Molecular weight formula_weight	71761.7 kDa
Source method src_method	nat
Copy count entity_count	1

Polymer Polymer

Polymer type type	polypeptide(L)
Chain IDs strand_id	A
Atom count atom_count	23250

KPRLLLFSPSVVHLGVPLSVGVQLQDVPRGQVVKGSVFLRNPSRNNVPCSPKVDFTLSSERDFALLSLQVPLKDAKSCGLHQLLRGPEVQLVAHSPWLKDSLSRTTNIQGINLLFSSRRGHLFLQTDQPIYNPGQRVRYRVFALDQKMRPSTDTITVMVENSHGLRVRKKEVYMPSSIFQDDFVIPDISEPGTWKISARFSDGLESNSSTQFEVKKYVLPNFEVKITPGKPYILTVPGHLDEMQLDIQARYIYGKPVQGVAYVRFGLLDEDGKKTFFRGLESQTKLVNGQSHISLSKAEFQDALEKLNMGITDLQGLRLYVAAAIIESPGGEMEEAELTSWYFVSSPFSLDLSKTKRHLVPGAPFLLQALVREMSGSPASGIPVKVSATVSSPGSVPEVQDIQQNTDGSGQVSIPIIIPQTISELQLSVSAGSPHPAIARLTVAAPPSGGPGFLSIERPDSRPPRVGDTLNLNLRAVGSGATFSHYYYMILSRGQIVFMNREPKRTLTSVSVFVDHHLAPSFYFVAFYYHGDHPVANSLRVDVQAGACEGKLELSVDGAKQYRNGESVKLHLETDSLALVALGALDTALYAAGSKSHKPLNMGKVFEAMNSYDLGCGPGGGDSALQVFQAAGLAFSDGDQWTLSRKRLSCPKEKTT

Entity 2 Entity 2 polymer

Description description	Complement C4 alpha chain
Molecular weight formula_weight	84270.1 kDa
Source method src_method	nat
Copy count entity_count	1

Polymer Polymer

Polymer type type	polypeptide(L)
Chain IDs strand_id	B

NVNFQKAINEKLGQYASPTAKRCCQDGVTRLPMMRSCEQRAARVQQPDCREPFLSCCQFAESLRKKSRDKGQAGLQRALEILQEEDLIDEDDIPVRSFFPENWLWRVETVDRFQILTLWLPDSLTTWEIHGLSLSKTKGLCVATPVQLRVFREFHLHLRLPMSVRRFEQLELRPVLYNYLDKNLTVSVHVSPVEGLCLAGGGGLAQQVLVPAGSARPVAFSVVPTAAAAVSLKVVARGSFEFPVGDAVSKVLQIEKEGAIHREELVYELNPLDHRGRTLEIPGNSDPNMIPDGDFNSYVRVTASDPLDTLGSEGALSPGGVASLLRLPRGCGEQTMIYLAPTLAASRYLDKTEQWSTLPPETKDHAVDLIQKGYMRIQQFRKADGSYAAWLSRDSSTWLTAFVLKVLSLAQEQVGGSPEKLQETSNWLLSQQQADGSFQDPCPVLDRSMQGGLVGNDETVALTAFVTIALHHGLAVFQDEGAEPLKQRVEASISKANSFLGEKASAGLLGAHAAAITAYALSLTKAPVDLLGVAHNNLMAMAQETGDNLYWGSVTGSQSNAVSPTPAPRNPSDPMPQAPALWIETTAYALLHLLLHEGKAEMADQASAWLTRQGSFQGGFRSTQDTVIALDALSAYWIASHTTEERGLNVTLSSTGRNGFKSHALQLNNRQIRGLEEELQFSLGSKINVKVGGNSKGTLKVLRTYNVLDMKNTTCQDLQIEVTVKGHVEYTMEANEDYEDYEYDELPAKDDPDAPLQPVTPLQLFEG

Entity 3 Entity 3 polymer

Description description	Complement C4 gamma chain
Molecular weight formula_weight	33115.6 kDa
Source method src_method	nat
Copy count entity_count	1

Polymer Polymer

Polymer type type	polypeptide(L)
Chain IDs strand_id	C

EAPKVVEEQESRVHYTVCIWRNGKVGLSGMAIADVTLLSGFHALRADLEKLTSLSDRYVSHFETEGPHVLLYFDSVPTSRECVGFEAVQEVPVGLVQPASATLYDYYNPERRCSVFYGAPSKSRLLATLCSAEVCQCAEGKCPRQRRALERGLQDEDGYRMKFACYYPRVEYGFQVKVLREDSRAAFRLFETKITQVLHFTKDVKAAANQMRNFLVRASCRLRLEPGKEYLIMGLDGATYDLEGHPQYLLDSNSWIEEMPSERLCRSTRQRAACAQLNDFLQEYGTQGCQV

Entity 4 Entity 4 polymer

Description description	Anti-C4b nanobody E3
Molecular weight formula_weight	14489.0 kDa
Source method src_method	man
Copy count entity_count	1

Polymer Polymer

Polymer type type	polypeptide(L)
Chain IDs strand_id	D

EVQLVESGGGLVQAGGSLRLSCAASGSDFSANAVGWYRQAPGKQRVVVASISSTGNTKYSNSVKGRFTISRDNAKNTVYLQMNSLKPEDTAVYYCWLFRFGIENYWGQGTQVTVSSHGSGLVPRGSGGGHHHHHH

Source Source

Source organism organism	Lama glama
Common name common_name	Llama
NCBI taxonomy ID ncbi_taxonomy_id	9844
Host organism host_organism	Escherichia coli

Entity 5 Entity 5 non-polymer

Description description	2-acetamido-2-deoxy-beta-D-glucopyranose
Molecular weight formula_weight	221.2 kDa
Source method src_method	syn
Copy count entity_count	4

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6. Fold Classification (SCOP + CATH) 5 domains

CATH v4.4 (5 domains)

Domain ID domain_id	7b2mA01
Class class	2 — Mainly Beta
Architecture architecture	60 — Sandwich
Topology topology	40 — Immunoglobulin-like
Homologous superfamily homologous superfamily	1930 — Macroglobulin (MG2) domain

Domain ID domain_id	7b2mA02
Class class	2 — Mainly Beta
Architecture architecture	60 — Sandwich
Topology topology	40 — Immunoglobulin-like
Homologous superfamily homologous superfamily	1930 — Macroglobulin (MG2) domain

Domain ID domain_id	7b2mA03
Class class	2 — Mainly Beta
Architecture architecture	60 — Sandwich
Topology topology	40 — Immunoglobulin-like
Homologous superfamily homologous superfamily	1940 —

Domain ID domain_id	7b2mC01
Class class	2 — Mainly Beta
Architecture architecture	60 — Sandwich
Topology topology	40 — Immunoglobulin-like
Homologous superfamily homologous superfamily	690 — Alpha-macroglobulin, receptor-binding domain

Domain ID domain_id	7b2mD01
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	1.000 Å
Unit-cell length b length_b	1.000 Å
Unit-cell length c length_c	1.000 Å
Unit-cell angle α angle_alpha	90.00 °
Unit-cell angle β angle_beta	90.00 °
Unit-cell angle γ angle_gamma	90.00 °
Molecules per unit cell Z z_pdb	—

Space group space_group	P 1
Space-group number int_tables_number	1
Crystal system crystal_system	—

Resolution resolution	3.39 Å
Resolution测定Method resolution_method	—
颗粒数 num_particles	176318

Cryo-EM structure of complement C4b in complex with nanobody E3

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

Complement C4 beta 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

7b2m__assembly_1__model_1

7b2m__assembly_1__model_1 | I(q)

7b2m__assembly_1__model_1 | P(r) · Pending

4. Crystallography and Experiment 4. Crystallography & Experiment

Unit cell Unit Cell

Symmetry Symmetry

冷冻电镜 EM 3D

5. Entities and Polymers Entities & Polymers (5)

Entity 1 Entity 1 polymer

Polymer Polymer

Entity 2 Entity 2 polymer

Polymer Polymer

Entity 3 Entity 3 polymer

Polymer Polymer

Entity 4 Entity 4 polymer

Polymer Polymer

Source Source

Entity 5 Entity 5 non-polymer

6. Fold Classification (SCOP + CATH) 5 domains

CATH v4.4 (5 domains)

7. Citations (1)

Cryo-EM structure of complement C4b in complex with nanobody E3

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

Complement C4 beta 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

7b2m__assembly_1__model_1

7b2m__assembly_1__model_1 | I(q)

7b2m__assembly_1__model_1 | P(r) · Pending

4. Crystallography and Experiment 4. Crystallography & Experiment

Unit cell Unit Cell

Symmetry Symmetry

冷冻电镜 EM 3D

5. Entities and Polymers Entities & Polymers (5)

Entity 1 Entity 1 polymer

Polymer Polymer

Entity 2 Entity 2 polymer

Polymer Polymer

Entity 3 Entity 3 polymer

Polymer Polymer

Entity 4 Entity 4 polymer

Polymer Polymer

Source Source

Entity 5 Entity 5 non-polymer

6. Fold Classification (SCOP + CATH) 5 domains

CATH v4.4 (5 domains)

7. Citations (1)