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Mutational substitution of residues implicated by crystal structure in binding the substrate glutathione to human glutathione S-transferase pi.
Authors:T H Manoharan  A M Gulick  P Reinemer  H W Dirr  R Huber  W E Fahl
Affiliation:McArdle Laboratory for Cancer Research, University of Wisconsin, Madison 53706.
Abstract:Site-directed substitution mutations were introduced into a cDNA expression vector (pUC120 pi) that encoded a human glutathione S-transferase pi isozyme to non-conservatively replace four residues (Tyr7, Arg13, Gln62 and Asp96). Our earlier X-ray crystallographic analysis implicated these residues in binding and/or chemically activating the substrate glutathione. Each substitution mutation decreased the specific activity of the enzyme to less than 2% of the wild-type. Glutathione-binding was also reduced; however, the Tyr7----Phe mutant still retained 27% of the wild-type capacity to bind glutathione, underlining the primary role that this residue is likely to play in chemically activating the glutathione molecule during catalysis.
Keywords:
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