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PDBsum entry 1oeu
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* Residue conservation analysis
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References listed in PDB file
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Key reference
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Title
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Oxidation state of the active-Site cysteine in protein tyrosine phosphatase 1b.
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Authors
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R.L.Van montfort,
M.Congreve,
D.Tisi,
R.Carr,
H.Jhoti.
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Ref.
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Nature, 2003,
423,
773-777.
[DOI no: ]
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PubMed id
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Abstract
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Protein tyrosine phosphatases regulate signal transduction pathways involving
tyrosine phosphorylation and have been implicated in the development of cancer,
diabetes, rheumatoid arthritis and hypertension. Increasing evidence suggests
that the cellular redox state is involved in regulating tyrosine phosphatase
activity through the reversible oxidization of the catalytic cysteine to
sulphenic acid (Cys-SOH). But how further oxidation to the irreversible
sulphinic (Cys-SO2H) and sulphonic (Cys-SO3H) forms is prevented remains
unclear. Here we report the crystal structures of the regulatory sulphenic and
irreversible sulphinic and sulphonic acids of protein tyrosine phosphatase 1B
(PTP1B), an important enzyme in the negative regulation of the insulin receptor
and a therapeutic target in type II diabetes and obesity. We also identify a
sulphenyl-amide species that is formed through oxidation of its catalytic
cysteine. Formation of the sulphenyl-amide causes large changes in the PTP1B
active site, which are reversible by reduction with the cellular reducing agent
glutathione. The sulphenyl-amide is a protective intermediate in the oxidative
inhibition of PTP1B. In addition, it may facilitate reactivation of PTP1B by
biological thiols and signal a unique state of the protein.
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Figure 1.
Figure 1: Comparison of native and sulphenyl-amide PTP1B. a,
Ribbon diagram of PTP1B. The phosphate-binding cradle is shown
in red, the WPD loop in green and the pTyr recognition loop in
gold. b, Superposition of native PTP1B (blue) and the
sulphenyl-amide-containing structure (orange), showing different
conformations of the pTyr recognition loop and the
phosphate-binding cradle. c, Electron density of the catalytic
cysteine and its neighbouring residues in reduced PTP1B (see
Supplementary Information). d, Electron density of the newly
identified sulphenyl-amide derivative of Cys 215. The electron
density maps in c and d are contoured at 1  .
All figures are generated using Aesop (M. Noble, Laboratory of
Molecular Biophysics, University of Oxford, unpublished).
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Figure 2.
Figure 2: Putative mechanism of sulphenyl-amide formation and
subsequent reactivation. The catalytic cysteine of PTP1B (E
-SH) is oxidized to a sulphenic acid (E -S -OH). The
sulphenyl-amide may be formed by a direct mechanism involving a
nucleophilic attack of the backbone nitrogen of Ser 216 on the S
 atom
of Cys 215 and subsequent release of water. Alternatively, the
sulphenic acid may be oxidized to a highly reactive intermediate
by H[2]O[2] or an oxidized thiol, which then reacts to give the
sulphenyl-amide. Reactivation of the enzyme occurs via mixed
disulphide formation with a thiol. R, glutathione or DTT; X,
leaving group OOH (sulphenoperoxoic acid) or OS(O)R
(sulphinothioic acid).
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The above figures are
reprinted
by permission from Macmillan Publishers Ltd:
Nature
(2003,
423,
773-777)
copyright 2003.
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Secondary reference #1
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Title
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Crystal structure of human protein tyrosine phosphatase 1b.
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Authors
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D.Barford,
A.J.Flint,
N.K.Tonks.
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Ref.
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Science, 1994,
263,
1397-1404.
[DOI no: ]
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PubMed id
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Secondary reference #2
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Title
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Redox regulation of protein tyrosine phosphatase 1b involves a sulphenyl-Amide intermediate.
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Authors
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A.Salmeen,
J.N.Andersen,
M.P.Myers,
T.C.Meng,
J.A.Hinks,
N.K.Tonks,
D.Barford.
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Ref.
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Nature, 2003,
423,
769-773.
[DOI no: ]
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PubMed id
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Figure 1.
Figure 1: Oxidation of PTP1B results in formation of a
sulphenyl-amide bond between Cys 215 and Ser 216. a, The PTP
loop in the sulphenyl-amide structure. Cyan, red and yellow
correspond to 2F[o] - F[c] and positive and negative F[o] - F[c]
electron density maps, respectively. The F[o] - F[c] density
indicates that there are no oxygen atoms attached to the Cys 215
S atom,
although a small amount of the enzyme is still reduced. b, Time
course of PTP1B oxidation. Electron density maps (2F[o] - F[c])
show the time-dependent changes at the catalytic Cys 215 of
PTP1B over a 16-h period. At 40 and 75 min, there is a mixture
of reduced and oxidized states. H[2]O[2] was in 100- to
1,000-fold molar excess over PTP1B. red, reduced; ox,
sulphenyl-amide structures. All figures were drawn with PYMOL
(see  fence
http://pymol.sourceforge.net/  fence
).
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Figure 2.
Figure 2: Conformational changes accompanying the oxidation of
PTP1B. a, Ribbon diagram showing catalytic site of reduced
PTP1B. The PTP loop is shown in red. b, Sulphenyl-amide species
of PTP1B in the same orientation as in a. c, Chemical mechanism
for generating the sulphenyl-amide bond. 'X:' denotes a
nucleophile. d, Superimposition of reduced (red) and
sulphenyl-amide (ox) states of PTP1B. Gly 218 is shown in
yellow. For clarity, the view has been rotated relative to a and
b.
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The above figures are
reproduced from the cited reference
with permission from Macmillan Publishers Ltd
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