Biological Assembly 1  

 3D View: Structure | Electron Density | Ligand Interaction

Standalone Viewers  
Protein Workshop | Ligand Explorer

Global Symmetry: Asymmetric - C1 
Global Stoichiometry: Hetero 6-mer - A5B 

Biological assembly 1 assigned by authors.

Macromolecule Content

• Total Structure Weight: 89493.78 
• Atom Count: 6096 
• Residue Count: 762 
• Unique protein chains: 2

1LT4

HEAT-LABILE ENTEROTOXIN MUTANT S63K

• DOI: 10.2210/pdb1LT4/pdb

• Classification: ENTEROTOXIN
• Organism(s): Musa acuminata, Escherichia coli
• Expression System: Escherichia coli
• Mutation(s): 1 


• Deposited: 1997-04-14 Released: 1997-06-16 
• Deposition Author(s): Van Den Akker, F., Hol, W.G.J.

---

Experimental Data Snapshot

• Method: X-RAY DIFFRACTION
• Resolution: 2 Å
• R-Value Free: 0.255 
• R-Value Work: 0.192 

Literature

Crystal structure of a non-toxic mutant of heat-labile enterotoxin, which is a potent mucosal adjuvant.

van den Akker, F., Pizza, M., Rappuoli, R., Hol, W.G.

(1997) Protein Sci. 6: 2650-2654

• PubMed: 9416617 
• DOI: 10.1002/pro.5560061220


• PubMed Abstract: 
  

Two closely related bacterial toxins, heat-labile enterotoxin (LT-I) and cholera toxin (CT), not only invoke a toxic activity that affects many victims worldwide but also contain a beneficial mucosal adjuvant activity that significantly enhances the potency of vaccines in general. For the purpose of vaccine design it is most interesting that the undesirable toxic activity of these toxins can be eliminated by the single-site mutation Ser63Lys in the A subunit while the mucosal adjuvant activity is still present. The crystal structure of the Ser63Lys mutant of LT-I is determined at 2.0 A resolution. Its structure appears to be essentially the same as the wild-type LT-I structure. The substitution Ser63Lys was designed, based on the wild-type LT-I crystal structure, to decrease toxicity by interfering with NAD binding and/or catalysis. In the mutant crystal structure, the newly introduced lysine side chain is indeed positioned such that it could potentially obstruct the productive binding mode of the substrate NAD while at the same time its positive charge could possibly interfere with the critical function of nearby charged groups in the active site of LT-I. The fact that the Ser63Lys mutant of LT-I does not disrupt the wild-type LT-I structure makes the non-toxic mutant potentially suitable, from a structural point of view, to be used as a vaccine to prevent enterotoxigenic E. coli infections. The structural similarity of mutant and wild-type toxin might also be the reason why the inactive Ser63Lys variant retains its adjuvant activity.

---

Related Citations: 

• Probing the Structure-Activity Relationship of Escherichia Coli Lt-A by Site-Directed Mutagenesis
  Pizza, M.,Domenighini, M.,Hol, W.,Giannelli, V.,Fontana, M.R.,Giuliani, M.M.,Magagnoli, C.,Peppoloni, S.,Manetti, R.,Rappuoli, R.
  (1994) Mol.Microbiol. 14: 51
• 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




---

Organizational Affiliation: 

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

Macromolecules

Find similar proteins by: Sequence  |  Structure

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

Entity ID: 2
Molecule	Chains	Sequence Length	Organism	Details
HEAT-LABILE ENTEROTOXIN	A	247	Musa acuminata	Mutation(s): 1  Gene Names: lt-A (K63)
Find proteins for Q2HQJ7 (Musa acuminata) Go to UniProtKB:  Q2HQJ7

Small Molecules

Ligands 2 Unique
ID	Chains	Name / Formula / InChI Key	2D Diagram & Interactions
BGC	D, E, F, G, H	BETA-D-GLUCOSE C6 H12 O6 WQZGKKKJIJFFOK-VFUOTHLCSA-N
GAL	D, E, F, G, H	BETA-D-GALACTOSE C6 H12 O6 WQZGKKKJIJFFOK-FPRJBGLDSA-N

Experimental Data & Validation

Experimental Data

• Method: X-RAY DIFFRACTION
• Resolution: 2 Å
• R-Value Free: 0.255 
• R-Value Work: 0.192 
• Space Group: P 2₁ 2₁ 2₁

Unit Cell:

Length (Å)	Angle (°)
a = 120.000	α = 90.00
b = 101.900	β = 90.00
c = 64.400	γ = 90.00

Software Package:

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

Structure Validation

Entry History 

Deposition Data

• Deposited Date: 1997-04-14 
• Released Date: 1997-06-16 
• Deposition Author(s): Van Den Akker, F., Hol, W.G.J.

Revision History 

• Version 1.0: 1997-06-16
  Type: Initial release
• Version 1.1: 2008-03-24
  Type: Version format compliance
• Version 1.2: 2011-07-13
  Type: Version format compliance