1tlf

UNPRECEDENTED QUATERNARY STRUCTURE OF E. COLI LAC REPRESSOR CORE TETRAMER: IMPLICATIONS FOR DNA LOOPING

Method: X-RAY DIFFRACTION

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

LAC REPRESSOR

Escherichia coli

State in the Current Structure

Assembly	Physical composition	Protein state	Molecular copy count	Associated components	Data consistency
1	Protein homooligomer	Homooligomer	Protein 4	ETHYL MERCURY ION × 4 1-methylethyl 1-thio-beta-D-galactopyranoside × 4	Consistent with protein count

Other States of the Same Protein in the Database

View Construct and Data Evidence

UniProt name	LACI_ECOLI
Isoform	—
PDB entities	1
Chains and sequence ranges	Author chain A； PDBConstruct 1–301； UniProt 19–319 Author chain B； PDBConstruct 1–301； UniProt 19–319 Author chain C； PDBConstruct 1–301； UniProt 19–319 Author chain D； PDBConstruct 1–301； UniProt 19–319

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	1tlf
Deposition date deposition_date	1995-03-06
Structure title title	UNPRECEDENTED QUATERNARY STRUCTURE OF E. COLI LAC REPRESSOR CORE TETRAMER: IMPLICATIONS FOR DNA LOOPING
Keywords keywords	TRANSCRIPTION REGULATION; TRANSCRIPTION REGULATION
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.

1tlf__assembly_1__model_1

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

Download this curve (.dat)

1tlf__assembly_1__model_1 | I(q)

100 plotted points; both axes use logarithmic scales.

1tlf__assembly_1__model_1 | P(r) · Pending

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

Rg（Guinier）	32.79 Å
Rg (electron density)	32.01 Å
Total Rg	32.51 Å
Atom count	10816
Residues	1184
Excluded volume	159640 Å³
Maximum q	0.500 Å⁻¹

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

Entity 1 Entity 1 polymer

Description description	LAC REPRESSOR
Molecular weight formula_weight	32154.7 kDa
Source method src_method	man
Copy count entity_count	4

Polymer Polymer

Polymer type type	polypeptide(L)
Chain IDs strand_id	A,B,C,D
Atom count atom_count	10816

QSLLIGVATSSLALHAPSQIVAAIKSRADQLGASVVVSMVERSGVEACKAAVHNLLAQRVSGLIINYPLDDQDAIAVEAACTNVPALFLDVSDQTPINSIIFSHEDGTRLGVEHLVALGHQQIALLAGPLSSVSARLRLAGWHKYLTRNQIQPIAEREGDWSAMSGFQQTMQMLNEGIVPTAMLVANDQMALGAMRAITESGLRVGADISVVGYDDTEDSSCYIPPLTTIKQDFRLLGQTSVDRLLQLSQGQAVKGNQLLPVSLVKRKTTLAPNTQTASPRALADSLMQLARQVSRLESGQ

Source Source

Source organism organism	Escherichia coli
NCBI taxonomy ID ncbi_taxonomy_id	562

Entity 2 Entity 2 non-polymer

Description description	ETHYL MERCURY ION
Molecular weight formula_weight	229.7 kDa
Source method src_method	syn
Copy count entity_count	4

Entity 3 Entity 3 non-polymer

Description description	1-methylethyl 1-thio-beta-D-galactopyranoside
Molecular weight formula_weight	238.3 kDa
Source method src_method	syn
Copy count entity_count	4

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6. Fold Classification (SCOP + CATH) 12 domains

SCOP 2.08 (4 domains)

Domain ID domain_id	d1tlfa_
Class class	c — Alpha and beta proteins (a/b)
Fold Fold fold	c.93 — Periplasmic binding protein-like I
Superfamily Superfamily superfamily	c.93.1 — Periplasmic binding protein-like I
Family Family family	c.93.1.1 — L-arabinose binding protein-like

Domain ID domain_id	d1tlfb_
Class class	c — Alpha and beta proteins (a/b)
Fold Fold fold	c.93 — Periplasmic binding protein-like I
Superfamily Superfamily superfamily	c.93.1 — Periplasmic binding protein-like I
Family Family family	c.93.1.1 — L-arabinose binding protein-like

Domain ID domain_id	d1tlfc_
Class class	c — Alpha and beta proteins (a/b)
Fold Fold fold	c.93 — Periplasmic binding protein-like I
Superfamily Superfamily superfamily	c.93.1 — Periplasmic binding protein-like I
Family Family family	c.93.1.1 — L-arabinose binding protein-like

Domain ID domain_id	d1tlfd_
Class class	c — Alpha and beta proteins (a/b)
Fold Fold fold	c.93 — Periplasmic binding protein-like I
Superfamily Superfamily superfamily	c.93.1 — Periplasmic binding protein-like I
Family Family family	c.93.1.1 — L-arabinose binding protein-like

CATH v4.4 (8 domains)

Domain ID domain_id	1tlfA01
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	1tlfA02
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	1tlfB01
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	1tlfB02
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	1tlfC01
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	1tlfC02
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	1tlfD01
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	1tlfD02
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	90.160 Å
Unit-cell length b length_b	64.730 Å
Unit-cell length c length_c	117.940 Å
Unit-cell angle α angle_alpha	90.00 °
Unit-cell angle β angle_beta	91.75 °
Unit-cell angle γ angle_gamma	90.00 °
Molecules per unit cell Z z_pdb	8

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

Resolution resolution	2.600 Å
Low-resolution limit resolution_low	— Å
R factor r_factor	0.2220
R_work r_work	0.2220
R_free r_free	—

UNPRECEDENTED QUATERNARY STRUCTURE OF E. COLI LAC REPRESSOR CORE TETRAMER: IMPLICATIONS FOR DNA LOOPING

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

LAC REPRESSOR

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

1tlf__assembly_1__model_1

1tlf__assembly_1__model_1 | I(q)

1tlf__assembly_1__model_1 | P(r) · Pending

4. Crystallography and Experiment 4. Crystallography & Experiment

Unit cell Unit Cell

Symmetry Symmetry

Refinement Refinement

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 non-polymer

6. Fold Classification (SCOP + CATH) 12 domains

SCOP 2.08 (4 domains)

CATH v4.4 (8 domains)

7. Citations (1)

UNPRECEDENTED QUATERNARY STRUCTURE OF E. COLI LAC REPRESSOR CORE TETRAMER: IMPLICATIONS FOR DNA LOOPING

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

LAC REPRESSOR

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

1tlf__assembly_1__model_1

1tlf__assembly_1__model_1 | I(q)

1tlf__assembly_1__model_1 | P(r) · Pending

4. Crystallography and Experiment 4. Crystallography & Experiment

Unit cell Unit Cell

Symmetry Symmetry

Refinement Refinement

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 non-polymer

6. Fold Classification (SCOP + CATH) 12 domains

SCOP 2.08 (4 domains)

CATH v4.4 (8 domains)

7. Citations (1)