P D McDonagh, D J Judah, J D Hayes, L Y Lian, G E Neal, C R Wolf, G C Roberts
Centre for Mechanisms of Human Toxicity, University of Leicester, Leicester LE1 9HN, UK.
The Biochemical journal 1999 Apr 1We have used homology modelling, based on the crystal structure of the human glutathione S-transferase (GST) A1-1, to obtain the three-dimensional structures of rat GSTA3 and rat GSTA5 subunits bound to S-aflatoxinyl-glutathione. The resulting models highlight two residues, at positions 208 and 108, that could be important for determining, either directly or indirectly, substrate specificity for aflatoxin-exo-8,9-epoxide among the Alpha-class GSTs. Residues at these positions were mutated in human GSTA1-1 (Met-208, Leu-108), rat GSTA3-3 (Glu-208, His-108) and rat GSTA5-5 (Asp-208, Tyr-108): in the active rat GSTA5-5 to those in the inactive GSTA1-1; and in the inactive human GSTA1-1 and rat GSTA3-3 to those in the active rat GSTA5-5. These studies show clearly that, in all three GSTs, an aspartate residue at position 208 is a prerequisite for high activity in aflatoxin-exo-8,9-epoxide conjugation, although this alone is not sufficient; other residues in the vicinity, particularly residues 103-112, are important, perhaps for the optimal orientation of the aflatoxin-exo-8,9-epoxide in the active site for catalysis to occur.
P D McDonagh, D J Judah, J D Hayes, L Y Lian, G E Neal, C R Wolf, G C Roberts. Determinants of specificity for aflatoxin B1-8,9-epoxide in alpha-class glutathione S-transferases. The Biochemical journal. 1999 Apr 1;339 ( Pt 1):95-101
PMID: 10085232
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