Molecular modeling of Bt Cry1Ac (DI-DII)-ASAL (Allium sativum lectin)-fusion protein and its interaction with aminopeptidase N (APN) receptor of Manduca sexta

J Mol Graph Model. 2012 Mar;33:61-76. doi: 10.1016/j.jmgm.2011.11.001. Epub 2011 Nov 23.


Genetic engineering of Bacillus thuringiensis (Bt) Cry proteins has resulted in the synthesis of various novel toxin proteins with enhanced insecticidal activity and specificity towards different insect pests. In this study, a fusion protein consisting of the DI-DII domains of Cry1Ac and garlic lectin (ASAL) has been designed in silico by replacing the DIII domain of Cry1Ac with ASAL. The binding interface between the DI-DII domains of Cry1Ac and lectin has been identified using protein-protein docking studies. Free energy of binding calculations and interaction profiles between the Cry1Ac and lectin domains confirmed the stability of fusion protein. A total of 18 hydrogen bonds was observed in the DI-DII-lectin fusion protein compared to 11 hydrogen bonds in the Cry1Ac (DI-DII-DIII) protein. Molecular mechanics/Poisson-Boltzmann (generalized-Born) surface area [MM/PB (GB) SA] methods were used for predicting free energy of interactions of the fusion proteins. Protein-protein docking studies based on the number of hydrogen bonds, hydrophobic interactions, aromatic-aromatic, aromatic-sulphur, cation-pi interactions and binding energy of Cry1Ac/fusion proteins with the aminopeptidase N (APN) of Manduca sexta rationalised the higher binding affinity of the fusion protein with the APN receptor compared to that of the Cry1Ac-APN complex, as predicted by ZDOCK, Rosetta and ClusPro analysis. The molecular binding interface between the fusion protein and the APN receptor is well packed, analogously to that of the Cry1Ac-APN complex. These findings offer scope for the design and development of customized fusion molecules for improved pest management in crop plants.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Bacillus thuringiensis Toxins
  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / metabolism
  • Binding Sites
  • CD13 Antigens / chemistry*
  • CD13 Antigens / metabolism
  • Endotoxins / chemistry*
  • Endotoxins / metabolism
  • Garlic / chemistry
  • Hemolysin Proteins / chemistry*
  • Hemolysin Proteins / metabolism
  • Hydrogen Bonding
  • Insect Proteins / chemistry
  • Insect Proteins / metabolism
  • Lectins / chemistry*
  • Lectins / metabolism
  • Manduca / enzymology*
  • Models, Molecular
  • Molecular Dynamics Simulation
  • Molecular Sequence Data
  • Protein Conformation
  • Protein Engineering
  • Protein Structure, Tertiary
  • Recombinant Fusion Proteins / chemistry*
  • Recombinant Fusion Proteins / metabolism*


  • Bacillus thuringiensis Toxins
  • Bacterial Proteins
  • Endotoxins
  • Hemolysin Proteins
  • Insect Proteins
  • Lectins
  • Recombinant Fusion Proteins
  • insecticidal crystal protein, Bacillus Thuringiensis
  • CD13 Antigens