2a1b

Carboxysome shell protein ccmK2

Method: X-RAY DIFFRACTION

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

Carbon dioxide concentrating mechanism protein ccmK homolog 2

Synechocystis sp.

State in the Current Structure

Assembly	Physical composition	Protein state	Molecular copy count	Associated components	Data consistency
1	Protein homooligomer	Homooligomer	Protein 6	No other associated polymer	Consistent with protein count
2	Protein homooligomer	Homooligomer	Protein 6	No other associated polymer	Consistent with protein count

Other States of the Same Protein in the Database

View Construct and Data Evidence

UniProt name	CCMK2_SYNY3
Isoform	—
PDB entities	1
Chains and sequence ranges	Author chain A； PDBConstruct 2–103； UniProt 1–102 Author chain B； PDBConstruct 2–103； UniProt 1–102 Author chain C； PDBConstruct 2–103； UniProt 1–102 Author chain D； PDBConstruct 2–103； UniProt 1–102 Author chain E； PDBConstruct 2–103； UniProt 1–102 Author chain F； PDBConstruct 2–103； UniProt 1–102 Author chain G； PDBConstruct 2–103； UniProt 1–102 Author chain H； PDBConstruct 2–103； UniProt 1–102 Author chain I； PDBConstruct 2–103； UniProt 1–102 Author chain J； PDBConstruct 2–103； UniProt 1–102 Author chain K； PDBConstruct 2–103； UniProt 1–102 Author chain L； PDBConstruct 2–103； UniProt 1–102

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	2a1b
Deposition date deposition_date	2005-06-20
Structure title title	Carboxysome shell protein ccmK2
Keywords keywords	cyclic hexamer; c6 point symmetry, carboxysome; carboxysome
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.

2a1b__assembly_1__model_1

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

Download this curve (.dat)

2a1b__assembly_1__model_1 | I(q)

100 plotted points; both axes use logarithmic scales.

2a1b__assembly_1__model_1 | P(r) · Pending

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

Rg（Guinier）	26.05 Å
Rg (electron density)	24.82 Å
Total Rg	25.67 Å
Atom count	4536
Residues	606
Excluded volume	80678 Å³
Maximum q	0.500 Å⁻¹

Assembly	Model	Structure unit	Oligomeric description	Status	CRYSOL	Actions
1	1	`2a1b__assembly_1__model_1`	hexameric （6）	Success	4.1.3-1-20251215 (887e7ef)	View Download
2	1	`2a1b__assembly_2__model_1`	hexameric （6）	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 (1)

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6. Fold Classification (SCOP + CATH) 24 domains

SCOP 2.08 (12 domains)

Domain ID domain_id	d2a1ba1
Class class	d — Alpha and beta proteins (a+b)
Fold Fold fold	d.58 — Ferredoxin-like
Superfamily Superfamily superfamily	d.58.56 — CcmK-like
Family Family family	d.58.56.1 — CcmK-like

Domain ID domain_id	d2a1bb_
Class class	d — Alpha and beta proteins (a+b)
Fold Fold fold	d.58 — Ferredoxin-like
Superfamily Superfamily superfamily	d.58.56 — CcmK-like
Family Family family	d.58.56.1 — CcmK-like

Domain ID domain_id	d2a1bc_
Class class	d — Alpha and beta proteins (a+b)
Fold Fold fold	d.58 — Ferredoxin-like
Superfamily Superfamily superfamily	d.58.56 — CcmK-like
Family Family family	d.58.56.1 — CcmK-like

Domain ID domain_id	d2a1bd_
Class class	d — Alpha and beta proteins (a+b)
Fold Fold fold	d.58 — Ferredoxin-like
Superfamily Superfamily superfamily	d.58.56 — CcmK-like
Family Family family	d.58.56.1 — CcmK-like

Domain ID domain_id	d2a1be_
Class class	d — Alpha and beta proteins (a+b)
Fold Fold fold	d.58 — Ferredoxin-like
Superfamily Superfamily superfamily	d.58.56 — CcmK-like
Family Family family	d.58.56.1 — CcmK-like

Domain ID domain_id	d2a1bf_
Class class	d — Alpha and beta proteins (a+b)
Fold Fold fold	d.58 — Ferredoxin-like
Superfamily Superfamily superfamily	d.58.56 — CcmK-like
Family Family family	d.58.56.1 — CcmK-like

Domain ID domain_id	d2a1bg_
Class class	d — Alpha and beta proteins (a+b)
Fold Fold fold	d.58 — Ferredoxin-like
Superfamily Superfamily superfamily	d.58.56 — CcmK-like
Family Family family	d.58.56.1 — CcmK-like

Domain ID domain_id	d2a1bh_
Class class	d — Alpha and beta proteins (a+b)
Fold Fold fold	d.58 — Ferredoxin-like
Superfamily Superfamily superfamily	d.58.56 — CcmK-like
Family Family family	d.58.56.1 — CcmK-like

Domain ID domain_id	d2a1bi_
Class class	d — Alpha and beta proteins (a+b)
Fold Fold fold	d.58 — Ferredoxin-like
Superfamily Superfamily superfamily	d.58.56 — CcmK-like
Family Family family	d.58.56.1 — CcmK-like

Domain ID domain_id	d2a1bj_
Class class	d — Alpha and beta proteins (a+b)
Fold Fold fold	d.58 — Ferredoxin-like
Superfamily Superfamily superfamily	d.58.56 — CcmK-like
Family Family family	d.58.56.1 — CcmK-like

Domain ID domain_id	d2a1bk_
Class class	d — Alpha and beta proteins (a+b)
Fold Fold fold	d.58 — Ferredoxin-like
Superfamily Superfamily superfamily	d.58.56 — CcmK-like
Family Family family	d.58.56.1 — CcmK-like

Domain ID domain_id	d2a1bl_
Class class	d — Alpha and beta proteins (a+b)
Fold Fold fold	d.58 — Ferredoxin-like
Superfamily Superfamily superfamily	d.58.56 — CcmK-like
Family Family family	d.58.56.1 — CcmK-like

CATH v4.4 (12 domains)

Domain ID domain_id	2a1bA00
Class class	3 — Alpha Beta
Architecture architecture	30 — 2-Layer Sandwich
Topology topology	70 — Alpha-Beta Plaits
Homologous superfamily homologous superfamily	1710 — BMC (bacterial microcompartment) domain

Domain ID domain_id	2a1bB00
Class class	3 — Alpha Beta
Architecture architecture	30 — 2-Layer Sandwich
Topology topology	70 — Alpha-Beta Plaits
Homologous superfamily homologous superfamily	1710 — BMC (bacterial microcompartment) domain

Domain ID domain_id	2a1bC00
Class class	3 — Alpha Beta
Architecture architecture	30 — 2-Layer Sandwich
Topology topology	70 — Alpha-Beta Plaits
Homologous superfamily homologous superfamily	1710 — BMC (bacterial microcompartment) domain

Domain ID domain_id	2a1bD00
Class class	3 — Alpha Beta
Architecture architecture	30 — 2-Layer Sandwich
Topology topology	70 — Alpha-Beta Plaits
Homologous superfamily homologous superfamily	1710 — BMC (bacterial microcompartment) domain

Domain ID domain_id	2a1bE00
Class class	3 — Alpha Beta
Architecture architecture	30 — 2-Layer Sandwich
Topology topology	70 — Alpha-Beta Plaits
Homologous superfamily homologous superfamily	1710 — BMC (bacterial microcompartment) domain

Domain ID domain_id	2a1bF00
Class class	3 — Alpha Beta
Architecture architecture	30 — 2-Layer Sandwich
Topology topology	70 — Alpha-Beta Plaits
Homologous superfamily homologous superfamily	1710 — BMC (bacterial microcompartment) domain

Domain ID domain_id	2a1bG00
Class class	3 — Alpha Beta
Architecture architecture	30 — 2-Layer Sandwich
Topology topology	70 — Alpha-Beta Plaits
Homologous superfamily homologous superfamily	1710 — BMC (bacterial microcompartment) domain

Domain ID domain_id	2a1bH00
Class class	3 — Alpha Beta
Architecture architecture	30 — 2-Layer Sandwich
Topology topology	70 — Alpha-Beta Plaits
Homologous superfamily homologous superfamily	1710 — BMC (bacterial microcompartment) domain

Domain ID domain_id	2a1bI00
Class class	3 — Alpha Beta
Architecture architecture	30 — 2-Layer Sandwich
Topology topology	70 — Alpha-Beta Plaits
Homologous superfamily homologous superfamily	1710 — BMC (bacterial microcompartment) domain

Domain ID domain_id	2a1bJ00
Class class	3 — Alpha Beta
Architecture architecture	30 — 2-Layer Sandwich
Topology topology	70 — Alpha-Beta Plaits
Homologous superfamily homologous superfamily	1710 — BMC (bacterial microcompartment) domain

Domain ID domain_id	2a1bK00
Class class	3 — Alpha Beta
Architecture architecture	30 — 2-Layer Sandwich
Topology topology	70 — Alpha-Beta Plaits
Homologous superfamily homologous superfamily	1710 — BMC (bacterial microcompartment) domain

Domain ID domain_id	2a1bL00
Class class	3 — Alpha Beta
Architecture architecture	30 — 2-Layer Sandwich
Topology topology	70 — Alpha-Beta Plaits
Homologous superfamily homologous superfamily	1710 — BMC (bacterial microcompartment) domain

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Unit-cell length a length_a	69.744 Å
Unit-cell length b length_b	179.987 Å
Unit-cell length c length_c	69.769 Å
Unit-cell angle α angle_alpha	90.00 °
Unit-cell angle β angle_beta	119.98 °
Unit-cell angle γ angle_gamma	90.00 °
Molecules per unit cell Z z_pdb	24

Space group space_group	P 1 21 1
Space-group number int_tables_number	4
Crystal system crystal_system	—

Resolution resolution	2.900 Å
Low-resolution limit resolution_low	89.990 Å
R factor r_factor	0.3130
R_work r_work	0.3130
R_free r_free	0.3460

Description description	Carbon dioxide concentrating mechanism protein ccmK homolog 2
Molecular weight formula_weight	12613.3 kDa
Mutation mutation	E52G
Source method src_method	man
Copy count entity_count	12

Polymer type type	polypeptide(L)
Chain IDs strand_id	A,B,C,D,E,F,G,H,I,J,K,L
Atom count atom_count	9072

Carboxysome shell protein ccmK2

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

Carbon dioxide concentrating mechanism protein ccmK homolog 2

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

2a1b__assembly_1__model_1

2a1b__assembly_1__model_1 | I(q)

2a1b__assembly_1__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 (1)

Entity 1 Entity 1 polymer

Polymer Polymer

Source Source

6. Fold Classification (SCOP + CATH) 24 domains

SCOP 2.08 (12 domains)

CATH v4.4 (12 domains)

7. Citations (1)

Source organism organism	Synechocystis sp.
NCBI taxonomy ID ncbi_taxonomy_id	1148
Host organism host_organism	Escherichia coli

Carboxysome shell protein ccmK2

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

Carbon dioxide concentrating mechanism protein ccmK homolog 2

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

2a1b__assembly_1__model_1

2a1b__assembly_1__model_1 | I(q)

2a1b__assembly_1__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 (1)

Entity 1 Entity 1 polymer

Polymer Polymer

Source Source

6. Fold Classification (SCOP + CATH) 24 domains

SCOP 2.08 (12 domains)

CATH v4.4 (12 domains)

7. Citations (1)