The molecular mechanism of hAl-1 glutathione S-transferase (GST) has been probed using fluorescence and NMR spectroscopy, kinetic analysis and X-ray crystallography. The results show that the mechanism of hAl-1 GST involves hydrophobic substrate activation, and the efficiency of this process is a crucial factor in hydrophobic substrate specificity. Hydrophobic substrate activation can only occur when the glutathione peptidyl moiety has bound, inducing a conformational change in the protein. The main region of the protein that is involved in this conformational change is the characteristic C-terminal helix of hAl-1 GST and the integrity of this region has been shown to be essential for hydrophobic substrate activation. It is thought that the C-terminal helix correctly orientates the hydrophobic substrate in the active site allowing activation to occur. The deletion of the C-terminal helix alters the substrate specificity of the enzyme, with the truncated enzyme having a high activity towards ethacrynic acid, normally a pi-class GST substrate. Thus the characteristic C-terminal helix of alpha class GSTs is a major determinant in substrate specificity, in particular determining the characteristic substrate specificity of hAl-1 GST.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:674511 |
| Date | January 1996 |
| Creators | Allardyce, Claire S. |
| Publisher | University of Leicester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/2381/35623 |
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