1CBY

DELTA-ENDOTOXIN


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.6 Å
  • R-Value Free: 0.261 
  • R-Value Work: 0.197 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

Structure of the mosquitocidal delta-endotoxin CytB from Bacillus thuringiensis sp. kyushuensis and implications for membrane pore formation.

Li, J.Koni, P.A.Ellar, D.J.

(1996) J.Mol.Biol. 257: 129-152

  • DOI: 10.1006/jmbi.1996.0152

  • PubMed Abstract: 
  • The delta-endotoxin CytB, found in parasporal inclusions of Bacillus thuringiensis subspecies kyushuensis, is a membrane pore-forming protein which is lethal to the larvae of Dipteran insects and broadly cytolytic in vitro. The crystal structure of C ...

    The delta-endotoxin CytB, found in parasporal inclusions of Bacillus thuringiensis subspecies kyushuensis, is a membrane pore-forming protein which is lethal to the larvae of Dipteran insects and broadly cytolytic in vitro. The crystal structure of CytB in the protoxin form has been determined by isomorphous replacement using heavy-atom derivatives of both the wild-type protein and an engineered cysteine mutant. The atomic model comprising residues 19 to 245 and 28 bound water molecules has been refined at 2.6 angstrom resolution to a crystallographic R-factor of 19.7% and a free R-factor of 26.1%. CytB has a single domain of alpha/beta architecture but a novel connectivity comprising two outer layers of alpha-helix hairpins wrapped around a mixed beta-sheet. In the protoxin form, CytB is a dimer linked by the intertwined N-terminal strands in a continuous, 12-stranded beta-sheet. Proteolytic processing cleaves the intertwined beta-strands to release the active CytB as a monomer, as well as removing the C-terminal tail to uncover the three-layered core. The homologous toxin CytA should show the same fold. Mutations in CytA that inhibit expression map to the dimer contacts and to the tip of helix pair A-B in contact with the sheet, apparently preventing correct folding. Mutations that inhibit toxicity map to the edge of the beta-sheet adjoining the helix pair C-D and to the sheet face, while mutations on the helix surfaces have no effect. Therefore segments forming the sheet, rather than the amphiphilic but short helices, are responsible for membrane binding and pore formation. A conformational change is postulated by which the helix pair C-D peels away from the sheet to lie on the membrane surface, while the sheet region rearranges to form an oligomeric trans-membrane pore.


    Related Citations: 
    • Crystallization of a Membrane Pore-Forming Protein with Mosquitocidal Activity from Bacillus Thuringiensis Subsp. Kyushuensis
      Li, J.,Koni, P.A.,Ellar, D.J.
      (1995) Proteins 23: 290
    • Biochemical Characterization of Bacillus Thuringiensis Cytolytic Delta-Endotoxins
      Koni, P.A.,Ellar, D.J.
      (1994) Microbiology (Reading, Engl.) 140: 1869
    • Cloning and Characterization of a Novel Bacillus Thuringiensis Cytolytic Delta-Endotoxin
      Koni, P.A.,Ellar, D.J.
      (1993) J.Mol.Biol. 229: 319


    Organizational Affiliation

    MRC Laboratory of Molecular Biology, Cambridge, UK.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
DELTA-ENDOTOXIN CYTB
A
259Bacillus thuringiensis subsp. kyushuensisGene Names: cyt2Aa1 (cytB)
Find proteins for Q04470 (Bacillus thuringiensis subsp. kyushuensis)
Go to UniProtKB:  Q04470
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.6 Å
  • R-Value Free: 0.261 
  • R-Value Work: 0.197 
  • Space Group: P 61 2 2
Unit Cell:
Length (Å)Angle (°)
a = 66.810α = 90.00
b = 66.810β = 90.00
c = 170.790γ = 120.00
Software Package:
Software NamePurpose
X-PLORrefinement
X-PLORphasing
X-PLORmodel building
MOSFLMdata reduction

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

  • Deposited Date: 1995-09-05 
  • Released Date: 1996-10-14 
  • Deposition Author(s): Li, J.

Revision History 

  • Version 1.0: 1996-10-14
    Type: Initial release
  • Version 1.1: 2008-03-24
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Derived calculations, Version format compliance