1LBG

LACTOSE OPERON REPRESSOR BOUND TO 21-BASE PAIR SYMMETRIC OPERATOR DNA, ALPHA CARBONS ONLY

• PDB DOI: https://doi.org/10.2210/pdb1LBG/pdb
• NAKB: 1LBG

• Classification: TRANSCRIPTION/DNA
• Organism(s): Escherichia coli
• Expression System: Escherichia coli
• Mutation(s): No 


• Deposited: 1996-01-03 Released: 1996-02-17 
• Deposition Author(s): Lewis, M., Chang, G., Horton, N.C., Kercher, M.A., Pace, H.C., Lu, P.

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Experimental Data Snapshot

• Method: X-RAY DIFFRACTION
• Resolution: 4.80 Å
• R-Value Work: 0.260 
• R-Value Observed: 0.260 

Literature

Crystal structure of the lactose operon repressor and its complexes with DNA and inducer.

Lewis, M., Chang, G., Horton, N.C., Kercher, M.A., Pace, H.C., Schumacher, M.A., Brennan, R.G., Lu, P.

(1996) Science 271: 1247-1254

• PubMed: 8638105 
• DOI: https://doi.org/10.1126/science.271.5253.1247
• Primary Citation of Related Structures:  
  1LBG, 1LBH, 1LBI


• PubMed Abstract: 
  

  The lac operon of Escherichia coli is the paradigm for gene regulation. Its key component is the lac repressor, a product of the lacI gene. The three-dimensional structures of the intact lac repressor, the lac repressor bound to the gratuitous inducer isopropyl-beta-D-1-thiogalactoside (IPTG) and the lac repressor complexed with a 21-base pair symmetric operator DNA have been determined. These three structures show the conformation of the molecule in both the induced and repressed states and provide a framework for understanding a wealth of biochemical and genetic information. The DNA sequence of the lac operon has three lac repressor recognition sites in a stretch of 500 base pairs. The crystallographic structure of the complex with DNA suggests that the tetrameric repressor functions synergistically with catabolite gene activator protein (CAP) and participates in the quaternary formation of repression loops in which one tetrameric repressor interacts simultaneously with two sites on the genomic DNA.

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Organizational Affiliation: 

Johnson Research Foundation, University of Pennsylvania, Philadelphia 19104, USA.

Biological Assembly 1  

Global Symmetry: Cyclic - C2  (Explore in 3D)
Global Stoichiometry: Homo 2-mer - A2 

Biological assembly 1 assigned by authors.

Biological Assembly 2  

Global Symmetry: Cyclic - C2  (Explore in 3D)
Global Stoichiometry: Homo 2-mer - A2 

Biological assembly 2 assigned by authors.

Macromolecule Content

• Total Structure Weight: 180.48 kDa 
• Atom Count: 3,144 
• Modelled Residue Count: 1,512 
• Deposited Residue Count: 1,524 
• Unique protein chains: 1
• Unique nucleic acid chains: 1

Macromolecules

Entity ID: 2
Molecule	Chains	Sequence Length	Organism	Details	Image
PROTEIN (LACTOSE OPERON REPRESSOR)	E [auth A], F [auth B], G [auth C], H [auth D]	360	Escherichia coli	Mutation(s): 0  Gene Names: LACI
UniProt
Find proteins for P03023 (Escherichia coli (strain K12)) Explore P03023  Go to UniProtKB:  P03023

Entity ID: 1
Molecule	Chains	Length	Organism	Image
DNA (5'-D(*GP*AP*AP*TP*TP*GP*TP*GP*AP*GP*CP*GP*CP*TP*CP*AP*CP*AP*AP*TP*T)-3')	A [auth E], B [auth F], C [auth G], D [auth H]	21	N/A

Experimental Data & Validation

Experimental Data

• Method: X-RAY DIFFRACTION
• Resolution: 4.80 Å
• R-Value Work: 0.260 
• R-Value Observed: 0.260 
• Space Group: C 1 2 1

Unit Cell:

Length ( Å )	Angle ( ˚ )
a = 104.3	α = 90
b = 224.4	β = 95.7
c = 112.1	γ = 90

Software Package:

Software Name	Purpose
X-PLOR	refinement
XDS	data reduction

Structure Validation

Entry History 

Deposition Data

• Released Date: 1996-02-17 
Deposition Author(s): Lewis, M., Chang, G., Horton, N.C., Kercher, M.A., Pace, H.C., Lu, P.

Revision History  

• Version 1.0: 1996-02-17
  Type: Initial release
  
• Version 1.1: 2008-05-22
  Changes: Version format compliance
• Version 1.2: 2011-07-13
  Changes: Version format compliance
• Version 1.3: 2024-02-14
  Changes: Data collection, Database references