SAXSdb — 1r8j

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

KaiA

Synechococcus elongatus PCC 7942

State in the Current Structure

Assembly	Physical composition	Protein state	Molecular copy count	Associated components	Data consistency
1	Protein homooligomer	Homooligomer	Protein 2	water × 2	Consistent with protein count

Other States of the Same Protein in the Database

View Construct and Data Evidence

UniProt name	KAIA_SYNP7
Isoform	—
PDB entities	1
Chains and sequence ranges	Author chain A； PDBConstruct 7–289； UniProt 2–284 Author chain B； PDBConstruct 7–289； UniProt 2–284

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	1r8j
Deposition date deposition_date	2003-10-26
Structure title title	Crystal Structure of Circadian Clock Protein KaiA from Synechococcus elongatus
Keywords keywords	KaiA, Circadian Clock Protein; CIRCADIAN CLOCK PROTEIN
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.

1r8j__assembly_1__model_1

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

Download this curve (.dat)

1r8j__assembly_1__model_1 | I(q)

100 plotted points; both axes use logarithmic scales.

1r8j__assembly_1__model_1 | P(r) · Pending

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

Rg（Guinier）	27.79 Å
Rg (electron density)	26.77 Å
Total Rg	27.61 Å
Atom count	4325
Residues	536
Excluded volume	77129 Å³
Maximum q	0.500 Å⁻¹

Assembly	Model	Structure unit	Oligomeric description	Status	CRYSOL	Actions
1	1	`1r8j__assembly_1__model_1`	dimeric （2）	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 (2)

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6. Fold Classification (SCOP + CATH) 10 domains

SCOP 2.08 (6 domains)

Domain ID domain_id	d1r8ja1
Class class	a — All alpha proteins
Fold Fold fold	a.186 — KaiA/RbsU domain
Superfamily Superfamily superfamily	a.186.1 — KaiA/RbsU domain
Family Family family	a.186.1.1 — Circadian clock protein KaiA, C-terminal domain

Domain ID domain_id	d1r8ja2
Class class	c — Alpha and beta proteins (a/b)
Fold Fold fold	c.23 — Flavodoxin-like
Superfamily Superfamily superfamily	c.23.1 — CheY-like
Family Family family	c.23.1.5 — N-terminal domain of the circadian clock protein KaiA

Domain ID domain_id	d1r8ja3
Class class	l — Artifacts
Fold Fold fold	l.1 — Tags
Superfamily Superfamily superfamily	l.1.1 — Tags
Family Family family	l.1.1.1 — Tags

Domain ID domain_id	d1r8jb1
Class class	a — All alpha proteins
Fold Fold fold	a.186 — KaiA/RbsU domain
Superfamily Superfamily superfamily	a.186.1 — KaiA/RbsU domain
Family Family family	a.186.1.1 — Circadian clock protein KaiA, C-terminal domain

Domain ID domain_id	d1r8jb2
Class class	c — Alpha and beta proteins (a/b)
Fold Fold fold	c.23 — Flavodoxin-like
Superfamily Superfamily superfamily	c.23.1 — CheY-like
Family Family family	c.23.1.5 — N-terminal domain of the circadian clock protein KaiA

Domain ID domain_id	d1r8jb3
Class class	l — Artifacts
Fold Fold fold	l.1 — Tags
Superfamily Superfamily superfamily	l.1.1 — Tags
Family Family family	l.1.1.1 — Tags

CATH v4.4 (4 domains)

Domain ID domain_id	1r8jA01
Class class	3 — Alpha Beta
Architecture architecture	40 — 3-Layer(aba) Sandwich
Topology topology	50 — Rossmann fold
Homologous superfamily homologous superfamily	2300 — Response regulator

Domain ID domain_id	1r8jA02
Class class	1 — Mainly Alpha
Architecture architecture	10 — Orthogonal Bundle
Topology topology	1240 — Methyltransferase, Methionine Synthase (B12-binding Domains); Chain A, domain 1
Homologous superfamily homologous superfamily	30 — KaiA/RbsU domain

Domain ID domain_id	1r8jB01
Class class	3 — Alpha Beta
Architecture architecture	40 — 3-Layer(aba) Sandwich
Topology topology	50 — Rossmann fold
Homologous superfamily homologous superfamily	2300 — Response regulator

Domain ID domain_id	1r8jB02
Class class	1 — Mainly Alpha
Architecture architecture	10 — Orthogonal Bundle
Topology topology	1240 — Methyltransferase, Methionine Synthase (B12-binding Domains); Chain A, domain 1
Homologous superfamily homologous superfamily	30 — KaiA/RbsU domain

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Unit-cell length a length_a	47.111 Å
Unit-cell length b length_b	125.818 Å
Unit-cell length c length_c	56.818 Å
Unit-cell angle α angle_alpha	90.00 °
Unit-cell angle β angle_beta	114.90 °
Unit-cell angle γ angle_gamma	90.00 °
Molecules per unit cell Z z_pdb	4

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

Resolution resolution	2.030 Å
Low-resolution limit resolution_low	20.000 Å
R factor r_factor	0.2131
R_work r_work	0.2101
R_free r_free	0.2714

Description description	KaiA
Molecular weight formula_weight	33135.7 kDa
Source method src_method	man
Copy count entity_count	2

Polymer type type	polypeptide(L)
Chain IDs strand_id	A,B
Atom count atom_count	4577

Crystal Structure of Circadian Clock Protein KaiA from Synechococcus elongatus

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

KaiA

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

1r8j__assembly_1__model_1

1r8j__assembly_1__model_1 | I(q)

1r8j__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 (2)

Entity 1 Entity 1 polymer

Polymer Polymer

Source Source

Entity 2 Entity 2 water

6. Fold Classification (SCOP + CATH) 10 domains

SCOP 2.08 (6 domains)

CATH v4.4 (4 domains)

7. Citations (1)

Source organism organism	Synechococcus elongatus PCC 7942
NCBI taxonomy ID ncbi_taxonomy_id	1140
Host organism host_organism	Escherichia coli BL21

Description description	water
Molecular weight formula_weight	18.0 kDa
Source method src_method	nat
Copy count entity_count	246

Crystal Structure of Circadian Clock Protein KaiA from Synechococcus elongatus

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

KaiA

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

1r8j__assembly_1__model_1

1r8j__assembly_1__model_1 | I(q)

1r8j__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 (2)

Entity 1 Entity 1 polymer

Polymer Polymer

Source Source

Entity 2 Entity 2 water

6. Fold Classification (SCOP + CATH) 10 domains

SCOP 2.08 (6 domains)

CATH v4.4 (4 domains)

7. Citations (1)