SAXSdb — 1k68

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

Phytochrome Response Regulator RcpA

Tolypothrix sp. PCC 7601

State in the Current Structure

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

Other States of the Same Protein in the Database

View Construct and Data Evidence

UniProt name	Q8RTN0_9CYAN
Isoform	—
PDB entities	1
Chains and sequence ranges	Author chain A； PDBConstruct 2–140； UniProt 9–147 Author chain B； PDBConstruct 2–140； UniProt 9–147

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	1k68
Deposition date deposition_date	2001-10-15
Structure title title	Crystal Structure of the Phosphorylated Cyanobacterial Phytochrome Response Regulator RcpA
Keywords keywords	phosphorylated aspartate, response regulator, chey homologue, homodimer, (beta/alpha)5, SIGNALING PROTEIN; SIGNALING 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.

1k68__assembly_1__model_1

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

Download this curve (.dat)

1k68__assembly_1__model_1 | I(q)

100 plotted points; both axes use logarithmic scales.

1k68__assembly_1__model_1 | P(r) · Pending

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

Rg（Guinier）	23.51 Å
Rg (electron density)	22.86 Å
Total Rg	23.52 Å
Atom count	2180
Residues	278
Excluded volume	39022 Å³
Maximum q	0.500 Å⁻¹

Assembly	Model	Structure unit	Oligomeric description	Status	CRYSOL	Actions
1	1	`1k68__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 (3)

Entity 1 Entity 1 polymer

Description description	Phytochrome Response Regulator RcpA
Molecular weight formula_weight	15862.0 kDa
Source method src_method	man
Copy count entity_count	2

Polymer Polymer

Polymer type type	polypeptide(L)
Chain IDs strand_id	A,B
Atom count atom_count	2295

AHKKIFLVEDNKADIRLIQEALANSTVPHEVVTVRDGMEAMAYLRQEGEYANASRPDLILLDLNLPKKDGREVLAEIKSDPTLKRIPVVVLSTSINEDDIFHSYDLHVNCYITKSANLSQLFQIVKGIEEFWLSTATLPS

Source Source

Source organism organism	Tolypothrix sp. PCC 7601
NCBI taxonomy ID ncbi_taxonomy_id	1188
Host organism host_organism	Escherichia coli

Entity 2 Entity 2 non-polymer

Description description	MAGNESIUM ION
Molecular weight formula_weight	24.3 kDa
Source method src_method	syn
Copy count entity_count	2

Entity 3 Entity 3 water

Description description	water
Molecular weight formula_weight	18.0 kDa
Source method src_method	nat
Copy count entity_count	113

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6. Fold Classification (SCOP + CATH) 4 domains

SCOP 2.08 (2 domains)

Domain ID domain_id	d1k68a_
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.23.1.1 — CheY-related

Domain ID domain_id	d1k68b_
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.23.1.1 — CheY-related

CATH v4.4 (2 domains)

Domain ID domain_id	1k68A00
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	1k68B00
Class class	3 — Alpha Beta
Architecture architecture	40 — 3-Layer(aba) Sandwich
Topology topology	50 — Rossmann fold
Homologous superfamily homologous superfamily	2300 — Response regulator

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Unit-cell length a length_a	76.700 Å
Unit-cell length b length_b	85.160 Å
Unit-cell length c length_c	44.050 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	8

Space group space_group	P 21 21 2
Space-group number int_tables_number	18
Crystal system crystal_system	—

Resolution resolution	1.900 Å
Low-resolution limit resolution_low	19.620 Å
R factor r_factor	0.2331
R_work r_work	0.2330
R_free r_free	0.2780

Crystal Structure of the Phosphorylated Cyanobacterial Phytochrome Response Regulator RcpA

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

Phytochrome Response Regulator RcpA

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

1k68__assembly_1__model_1

1k68__assembly_1__model_1 | I(q)

1k68__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 (3)

Entity 1 Entity 1 polymer

Polymer Polymer

Source Source

Entity 2 Entity 2 non-polymer

Entity 3 Entity 3 water

6. Fold Classification (SCOP + CATH) 4 domains

SCOP 2.08 (2 domains)

CATH v4.4 (2 domains)

7. Citations (1)

Crystal Structure of the Phosphorylated Cyanobacterial Phytochrome Response Regulator RcpA

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

Phytochrome Response Regulator RcpA

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

1k68__assembly_1__model_1

1k68__assembly_1__model_1 | I(q)

1k68__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 (3)

Entity 1 Entity 1 polymer

Polymer Polymer

Source Source

Entity 2 Entity 2 non-polymer

Entity 3 Entity 3 water

6. Fold Classification (SCOP + CATH) 4 domains

SCOP 2.08 (2 domains)

CATH v4.4 (2 domains)

7. Citations (1)