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PDBsum entry 1xwg
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References listed in PDB file
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Key reference
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Title
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New crystal structures of human glutathione transferase a1-1 shed light on glutathione binding and the conformation of the c-Terminal helix.
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Authors
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E.Grahn,
M.Novotny,
E.Jakobsson,
A.Gustafsson,
L.Grehn,
B.Olin,
D.Madsen,
M.Wahlberg,
B.Mannervik,
G.J.Kleywegt.
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Ref.
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Acta Crystallogr D Biol Crystallogr, 2006,
62,
197-207.
[DOI no: ]
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PubMed id
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Abstract
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Human glutathione transferase A1-1 is a well studied enzyme, but despite a
wealth of structural and biochemical data a number of aspects of its catalytic
function are still poorly understood. Here, five new crystal structures of this
enzyme are described that provide several insights. Firstly, the structure of a
complex of the wild-type human enzyme with glutathione was determined for the
first time at 2.0 angstroms resolution. This reveals that glutathione binds in
the G site in a very similar fashion as the glutathione portion of substrate
analogues in other structures and also that glutathione binding alone is
sufficient to stabilize the C-terminal helix of the protein. Secondly, we have
studied the complex with a decarboxylated glutathione conjugate that is known to
dramatically decrease the activity of the enzyme. The T68E mutant of human
glutathione transferase A1-1 recovers some of the activity that is lost with the
decarboxylated glutathione, but our structures of this mutant show that none of
the earlier explanations of this phenomenon are likely to be correct. Thirdly,
and serendipitously, the apo structures also reveal the conformation of the
crucial C-terminal region that is disordered in all previous apo structures. The
C-terminal region can adopt an ordered helix-like structure even in the apo
state, but shows a strong tendency to unwind. Different conformations of the
C-terminal regions were observed in the apo states of the two monomers, which
suggests that cooperativity could play a role in the activity of the enzyme.
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Figure 2.
Figure 2
Crystal structure of human GST A1-1 with only glutathione bound. (a) The homodimer shown
in a ribbon representation. The view is along the twofold axis that relates the two
subunits. (b) The A subunit with secondary-structure elements labelled. Figs. 2, 3 and 4
were created using Swiss-PDB Viewer 3.7 (Guex & Peitsch, 1997 [Guex, N. & Peitsch, M.
C. (1997). Electrophoresis, 18, 2714-2723.]) and POV-Ray 3.6 for
Windows (http://www.povray.org/ ).
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Figure 5.
Figure 5
Superposition of the C-terminal regions of various GST A1-1 structures. (a) Eight
different GST A1-1 structures (16 monomers; PDB codes 1guh , 1gse and 1gsf
, as well as the five structures reported here) were superimposed (using the C^
 atoms of residues 2-209). Four structures with a glutathione conjugate bound
are shown in red, the two apo structures in yellow, the structure with only glutathione
bound in blue and the structure with ethacrynic acid bound in green. (b) Superposition of
the C-terminal regions of the two apo structures presented here. A monomers are shown in
red and B monomers in yellow. Figs. 5 and 6 were created with PyMOL
(http://www.pymol.org/ ).
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The above figures are
reprinted
by permission from the IUCr:
Acta Crystallogr D Biol Crystallogr
(2006,
62,
197-207)
copyright 2006.
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