1ydk
From Proteopedia
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Crystal structure of the I219A mutant of human glutathione transferase A1-1 with S-hexylglutathione
Overview
The C-terminal region in class Alpha glutathione transferase A1-1, (GSTA1-1), which forms an amphipathic alpha-helix (helix 9), is known to, contribute to the catalytic and non-substrate ligand-binding functions of, the enzyme. The region in the apo protein is proposed to be disordered, which, upon ligand binding at the active-site, becomes structured and, localised. Because Ile219 plays a pivotal role in the stability and, localisation of the region, the role of tertiary interactions mediated by, Ile219 in determining the conformation and dynamics of the C-terminal, region were studied. Ligand-binding microcalorimetric and X-ray structural, data were obtained to characterise ligand binding at the active-site and, the associated localisation of the C-terminal region. In the crystal, structure of the I219A hGSTA1-1.S-hexylglutathione complex, the C-terminal, region of one chain is mobile and not observed (unresolved electron, density), whereas the corresponding region of the other chain is localised, and structured as a result of crystal packing interactions. In solution, the mutant C-terminal region of both chains in the complex is mobile and, delocalised resulting in a hydrated, less hydrophobic active-site and a, reduction in the affinity of the protein for S-hexylglutathione. Complete, dehydration of the active-site, important for maintaining the highly, reactive thiolate form of glutathione, requires the binding of ligands and, the subsequent localisation of the C-terminal region. Thermodynamic data, demonstrate that the mobile C-terminal region in apo hGSTA1-1 is, structured and does not undergo ligand-induced folding. Its close, proximity to the surface of the wild-type protein is indicated by the, concurrence between the observed heat capacity change of complex formation, and the type and amount of surface area that becomes buried at the, ligand-protein interface when the C-terminal region in the apo protein, assumes the same localised structure as that observed in the wild-type, complex.
About this Structure
1YDK is a Single protein structure of sequence from Homo sapiens with GTX as ligand. Active as Glutathione transferase, with EC number 2.5.1.18 Full crystallographic information is available from OCA.
Reference
Tertiary interactions stabilise the C-terminal region of human glutathione transferase A1-1: a crystallographic and calorimetric study., Kuhnert DC, Sayed Y, Mosebi S, Sayed M, Sewell T, Dirr HW, J Mol Biol. 2005 Jun 17;349(4):825-38. PMID:15893769
Page seeded by OCA on Mon Nov 12 20:18:32 2007
