Biological Assembly 1  

 3D View: Structure | 1D-3D View | Electron Density | Validation Report

Global Symmetry: Asymmetric - C1 
Global Stoichiometry: Hetero 6-mer - A5B1 Local Symmetry: Cyclic - C5  (3D View)
Local Stoichiometry: Homo 5-mer - A5 

Local Symmetry: Cyclic - C5  (3D View)
Local Stoichiometry: Homo 5-mer - A5 

Biological assembly 1 assigned by authors and generated by PISA (software)

Macromolecule Content

• Total Structure Weight: 88.64 kDa 
• Atom Count: 6093 
• Modelled Residue Count: 741 
• Deposited Residue Count: 755 
• Unique protein chains: 2

1LT3

HEAT-LABILE ENTEROTOXIN DOUBLE MUTANT N40C/G166C

• PDB DOI: 10.2210/pdb1LT3/pdb

• Classification: ENTEROTOXIN
• Organism(s): Escherichia coli
• Expression System: Escherichia coli
• Mutation(s): Yes 


• Deposited: 1997-04-12 Released: 1997-07-07 
• Deposition Author(s): Van Den Akker, F., Hol, W.G.J.

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Experimental Data Snapshot

• Method: X-RAY DIFFRACTION
• Resolution: 2.00 Å
• R-Value Free: 0.261 
• R-Value Work: 0.188 
• R-Value Observed: 0.188 

Literature

Crystal structure of heat-labile enterotoxin from Escherichia coli with increased thermostability introduced by an engineered disulfide bond in the A subunit.

van den Akker, F., Feil, I.K., Roach, C., Platas, A.A., Merritt, E.A., Hol, W.G.

(1997) Protein Sci 6: 2644-2649

• PubMed: 9416616 
• DOI: 10.1002/pro.5560061219
• Primary Citation of Related Structures:  
  1LT3


• PubMed Abstract: 
  

Cholera toxin (CT) produced by Vibrio cholerae and heat-labile enterotoxin (LT-I), produced by enterotoxigenic Escherichia coli, are AB5 heterohexamers with an ADP-ribosylating A subunit and a GM1 receptor binding B pentamer. These toxins are among the most potent mucosal adjuvants known and, hence, are of interest both for the development of anti-diarrheal vaccines against cholera or enterotoxigenic Escherichia coli diarrhea and also for vaccines in general. However, the A subunits of CT and LT-I are known to be relatively temperature sensitive. To improve the thermostability of LT-I an additional disulfide bond was introduced in the A1 subunit by means of the double mutation N40C and G166C. The crystal structure of this double mutant of LT-I has been determined to 2.0 A resolution. The protein structure of the N40C/G166C double mutant is very similar to the native structure except for a few local shifts near the new disulfide bond. The introduction of this additional disulfide bond increases the thermal stability of the A subunit of LT-I by 6 degrees C. The enhancement in thermostability could make this disulfide bond variant of LT-I of considerable interest for the design of enterotoxin-based vaccines.

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Related Citations: 

• Refined Structure of Escherichia Coli Heat-Labile Enterotoxin, a Close Relative of Cholera Toxin
  Sixma, T.K., Kalk, K.H., Van Zanten, B.A., Dauter, Z., Kingma, J., Witholt, B., Hol, W.G.
  (1993) J Mol Biol 230: 890

• Crystal Structure of a Cholera Toxin-Related Heat-Labile Enterotoxin from E. Coli
  Sixma, T.K., Pronk, S.E., Kalk, K.H., Wartna, E.S., Van Zanten, B.A., Witholt, B., Hol, W.G.
  (1991) Nature 351: 371

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Organizational Affiliation: 

Department of Biochemistry, University of Washington, Seattle 98195-7420, USA.

Macromolecules

Entity ID: 1
Molecule	Chains	Sequence Length	Organism	Details	Image
HEAT-LABILE ENTEROTOXIN	A [auth D], B [auth E], C [auth F], D [auth G], E [auth H]	103	Escherichia coli	Mutation(s): 0  Gene Names: eltB, ltpB
UniProt
Find proteins for P32890 (Escherichia coli) Explore P32890  Go to UniProtKB:  P32890

Entity ID: 2
Molecule	Chains	Sequence Length	Organism	Details	Image
HEAT-LABILE ENTEROTOXIN	F [auth A]	240	Escherichia coli	Mutation(s): 2  Gene Names: eltA, ltpA
UniProt
Find proteins for P06717 (Escherichia coli) Explore P06717  Go to UniProtKB:  P06717

Oligosaccharides

Help

Entity ID: 3
Molecule	Chains	Chain Length	2D Diagram	Glycosylation
beta-D-galactopyranose-(1-4)-beta-D-glucopyranose	G [auth B], H [auth C], I, J, K	2		N/A
Glycosylation Resources
GlyTouCan:  G84224TW GlyCosmos:  G84224TW GlyGen:  G84224TW

Biologically Interesting Molecules (External Reference) 1 Unique

Entity ID: 3
ID	Chains	Name	Type/Class	2D Diagram	3D Interactions
PRD_900004	G [auth B], H [auth C], I, J, K	beta-lactose	Oligosaccharide / Nutrient		Ligand Interaction

Experimental Data & Validation

Experimental Data

• Method: X-RAY DIFFRACTION
• Resolution: 2.00 Å
• R-Value Free: 0.261 
• R-Value Work: 0.188 
• R-Value Observed: 0.188 
• Space Group: P 2₁ 2₁ 2₁

Unit Cell:

Length ( Å )	Angle ( ˚ )
a = 119.7	α = 90
b = 101.1	β = 90
c = 64.2	γ = 90

Software Package:

Software Name	Purpose
DENZO	data reduction
SCALEPACK	data scaling
X-PLOR	model building
X-PLOR	refinement
X-PLOR	phasing

Structure Validation

Entry History 

Deposition Data

• Deposited Date: 1997-04-12 
• Released Date: 1997-07-07 
Deposition Author(s): Van Den Akker, F., Hol, W.G.J.

Revision History  

• Version 1.0: 1997-07-07
  Type: Initial release
  
• Version 1.1: 2008-03-24
  Changes: Version format compliance
• Version 1.2: 2011-07-13
  Changes: Version format compliance
• Version 2.0: 2020-07-29
  Type: Remediation
  Reason: Carbohydrate remediation
  Changes: Atomic model, Data collection, Derived calculations, Structure summary
• Version 2.1: 2021-11-03
  Changes: Database references, Structure summary