1LTS

REFINED STRUCTURE OF E. COLI HEAT LABILE ENTEROTOXIN, A CLOSE RELATIVE OF CHOLERA TOXIN


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.95 Å

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

Refined structure of Escherichia coli heat-labile enterotoxin, a close relative of cholera toxin.

Sixma, T.K.Van Zanten, B.A.M.Dauter, Z.Hol, W.G.J.

(1993) J.Mol.Biol. 230: 890-918

  • DOI: 10.1006/jmbi.1993.1209

  • PubMed Abstract: 
  • Heat-labile enterotoxin (LT) from Escherichia coli is a bacterial protein toxin with an AB5 multimer structure, in which the B pentamer has a membrane binding function and the A subunit is needed for enzymatic activity. The LT crystal structure has b ...

    Heat-labile enterotoxin (LT) from Escherichia coli is a bacterial protein toxin with an AB5 multimer structure, in which the B pentamer has a membrane binding function and the A subunit is needed for enzymatic activity. The LT crystal structure has been solved using a combination of multiple isomorphous replacement, fivefold averaging and molecular dynamics refinement. Phase combination using all these sources of phase information was of crucial importance for the chain tracing. The structure has now been refined to 1.95 A resolution, resulting in a model containing 6035 protein atoms and 293 solvent molecules with a crystallographic R-factor of 18.2% and good stereochemistry. The B subunits are arranged as a highly stable pentamer with a donut shape. Each subunit takes part in approximately 30 inter-subunit hydrogen bonds and six salt bridges with its two neighbors, whilst burying a large surface area. The A subunit has higher temperature factors and less well-defined secondary structure than the B subunits. It interacts with the B pentamer mainly via the C-terminal A2 fragment, which runs through the highly charged central pore of the B subunits. The pore contains at least 66 water molecules, which fill the space left by the A2 fragment. A detailed analysis of the contacts between A and B subunits showed that most specific contacts occur at the entrance of the central pore of the B pentamer, while the contacts within the pore are mainly hydrophobic and water mediated, with the exception of two salt bridges. Only a few contacts exist between the A1 fragment and the B pentamer, showing that the A2 fragment functions as a "linker" of the A and B parts of the protein. Interacting with the A subunit by the B subunits does not cause large deviations from a common B subunit structure, and the 5-fold symmetry is well maintained. A potential NAD(+)-binding site is located in an elongated crevice at the interface of two small sheets in the A1 fragment. At the back of this crevice the functionally important Arg7 makes a hydrogen bond connecting two strands, which seems to be conserved across the ADP-ribosylating toxin family. The putative catalytic residue (A1:Glu112) is located nearby, close to a very hydrophobic region, which packs two loops together. This hydrophobic region may be important for catalysis and membrane translocation.


    Related Citations: 
    • 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.M.,Witholt, B.,Hol, W.G.J.
      (1991) Nature 351: 371
    • Lactose Binding to Heat-Labile Enterotoxin Revealed by X-Ray Crystallography
      Sixma, T.K.,Pronk, S.E.,Kalk, K.H.,Van Zanten, B.A.M.,Berghuis, A.M.,Hol, W.G.J.
      (1992) Nature 355: 561
    • Native Non-Isomorphism in the Structure Determination of Heat Labile Enterotoxin (Lt) from E. Coli
      Sixma, T.K.,Pronk, S.E.,Van Scheltinga, A.C.T.,Aguirre, A.,Kalk, K.H.,Vriend, G.,Hol, W.G.J.
      (1991) Proceedings Ccp4 Study Weekend: Isomorphous Replacement and Anomalous Scattering 29: 133


    Organizational Affiliation

    BIOSON Research Institute, University of Groningen, The Netherlands.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
HEAT-LABILE ENTEROTOXIN, SUBUNIT B
D, E, F, G, H
103Escherichia coliMutation(s): 0 
Gene Names: eltB (ltpB)
Find proteins for P32890 (Escherichia coli)
Go to UniProtKB:  P32890
Entity ID: 2
MoleculeChainsSequence LengthOrganismDetails
HEAT-LABILE ENTEROTOXIN, SUBUNIT A
A
185Escherichia coliMutation(s): 0 
Gene Names: eltA (ltpA)
Find proteins for P06717 (Escherichia coli)
Go to UniProtKB:  P06717
Entity ID: 3
MoleculeChainsSequence LengthOrganismDetails
HEAT-LABILE ENTEROTOXIN, SUBUNIT A
C
41Escherichia coliMutation(s): 0 
Gene Names: eltA (ltpA)
Find proteins for P06717 (Escherichia coli)
Go to UniProtKB:  P06717
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.95 Å
  • Space Group: P 21 21 21
Unit Cell:
Length (Å)Angle (°)
a = 119.200α = 90.00
b = 98.200β = 90.00
c = 64.800γ = 90.00
Software Package:
Software NamePurpose
TNTrefinement
X-PLORmodel building
X-PLORphasing
X-PLORrefinement

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 1994-01-31
    Type: Initial release
  • Version 1.1: 2008-03-24
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Version format compliance