Delta - endotoxins structure database

Martins, N.F.(1), Togawa, R.C.(1), Batista, J.A.N.(2), Oliveira, O.B.N.(2), Dias, S.C.(2), Silva, S.M.B.(2), Fragoso, R.R.(2),  Quezado, M.(2), Grossi de Sa, M.F.(2)

(1)Laboratório de Bioinformática, EMBRAPA - Recursos Genéticos e Biotecnologia, Brasília, DF, Brasil. (2)Laboratório de Biologia Molecular EMBRAPA - Recursos Genéticos e Biotecnologia, Brasília, DF, Brasil.

The delta endotoxin (or cry protein) are produced in great variety with different species of Bacillus thuringiensis. Some proteins are specific against insects in the orders Lepidoptera, Diptera and Coleoptera. Once ingested by the host, the toxin are activated by gut proteases. The active protoxins bind to receptors on the brush border of the intestinal epithelium and create `leakage channels' of a diameter of about 10-20 angstroms. This subsequently leads to insect death due to starvation and septicemia. The toxicology data provided nowadays are sufficient to demonstrate the specificity but not the mode of action of delta-endotoxins. Although all the effects and benefits are well established around the world there is still a remain question about the mechanism of action at the molecular level.  Actually, the database has around 100 genes, but only 5 three dimensional structures are available in the PDB databank.  Detailed structural and biochemical knowledge of BT delta-endotoxins would permit the redesign of these toxins to customize host range, alter activity, improve stability etc. In this context, genetic engineering and molecular modeling together are able to add some important information about the structure and function relationship. This work presents the structural databases of 50 delta-endotoxins from different families. The major goal was to build a molecular modeling databank which will allow further studies at the atomic level. All models were built using MODELLER and validated by PROCHECK and PROSA II. The structure –function relationship is discussed and the families conserve in their structures singular features that may explain the specificity of the toxins.

CORRESPONDENCE TO:

Natália Florêncio Martins, R. 9 Norte Bloco 4 ap. 1202, Aguas Claras, Brasilia, DF, CEP: 70.000-000, Brasil, Email: natalia@cenargen.embrapa.br