03631nam a2200253 a 450000100080000000500110000800800410001910000150006024501390007526001760021430000110039050000390040152027500044065000130319065000190320365000280322265000130325065300200326370000210328370000170330470000210332170000160334270000190335810087542020-01-17       2005    bl uuuu     u00u1 u    #d1 aGUELFI, A.  aMolecular dynamics analysis of glutathione transferases sugarcane mutants and their interactions with atrazine.h[electronic resource]  aIn: X-MEETING; INTERNATIONAL CONFERENCE OF THE AB3C, 1., 2005, Caxambu. [Proceedings...]. [S.l.]: Associação Brasileira de Bioinformática e Biologia Computacionalc2005  ap. 94.  aX-meeting 2005. Presented posters.  aThe glutathione transferases (GSTs; EC 2.5.1.18) consist of soluble and dimeric proteins, which are important in the metabolism of drugs and xenobiotics. GSTs have been found in virtually all plants, vertebrates, insects, yeasts and bacteria. These enzymes, with approximately 50 kDa, catalyze the conjugation of glutathione (GSH; gamma-Glu-Cys-Gly) with a broad variety of electrophilic compounds. The active site of these enzymes consists of two domains, the G-site where glutathione is attached and the H-site, the hydrophobic binding pocket. In crops, many herbicide families are susceptible to glutathione conjugation like triazinones, sulfonylureas and thiocarbamates. This conjugation is one of the major mechanisms of resistance found in plants, which protects plants from the presence of herbicides. One example is the accelerated atrazine detoxifícation via GSH conjugation in the resistant biotype of some weeds, due to enhanced kcat for GST activity. The knowledge of the mechanisms of resistance is important for the development of resistant varieties of commercial crops. Therefore, the present work aimed to characterize the ligand pocket of sugarcane GST I, propose mutants and analyze the interactions with the herbicide atrazine. The molecular modelings of mutants GST were carried out with Modeller 7v7. The program Gromacs 3.2 was used for energy minimization and molecular dynamics. STING was used for GST characterization and LPC software for GST-atrazine interactions of the proposed mutants. The analyses showed five main residues that might be important for the atrazine specificity: Leu10, Trp12, Phe35, Phe114 and Ile118. A molecular dynamics was used to study the mutants. First, each one of these residues was mutated for Ala. Second, once at a time the aliphatic (Leu, Ile) was changed for Phe and the aromatic (Phe, Trp) for Leu. Analyses at the ligand pocket residues, types of interactions, and the trajectories showed three mutations that could improve the GST catalyses. These mutations are Leu10Phe, Trp12Leu and Phe114Leu. Leu10Phe caused the occurrence of hydrophobic interactions between Phe10 with Met208, which reduced the strong influences of Trp12 at the active site. The mutation Trp12Leu removed the aromatic interferences between Trp12 and the aromatic ring of atrazine. A similar effect was seen with Phe114Leu. The mutation Phe35Leu suggested great instability, which agrees with literature. Finally, the substitution Ile118Phe introduced several aromatic interactions at the active site, increasing the affinity for atrazine and reducing the catalytic efficiency of GST. In order to confirm our observations, we are now working in the analyses "in vitro" in Centro de Tecnologia Canaviera (CTC).  aAtrazine  aBioinformatics  aGlutathione transferase  aAtrazina  aBioinformática1 aCHABREGAS, S. M.1 aFALCO, M. C.1 aFALCAO, P. R. K.1 aNESHICH, G.1 aAZEVEDO, R. A.