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PDBsum entry 2baq
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References listed in PDB file
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Key reference
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Title
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Prevention of mkk6-Dependent activation by binding to p38alpha map kinase.
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Authors
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J.E.Sullivan,
G.A.Holdgate,
D.Campbell,
D.Timms,
S.Gerhardt,
J.Breed,
A.L.Breeze,
A.Bermingham,
R.A.Pauptit,
R.A.Norman,
K.J.Embrey,
J.Read,
W.S.Vanscyoc,
W.H.Ward.
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Ref.
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Biochemistry, 2005,
44,
16475-16490.
[DOI no: ]
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PubMed id
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Abstract
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Inhibition of p38alpha MAP kinase is a potential approach for the treatment of
inflammatory disorders. MKK6-dependent phosphorylation on the activation loop of
p38alpha increases its catalytic activity and affinity for ATP. An inhibitor,
BIRB796, binds at a site used by the purine moiety of ATP and extends into a
"selectivity pocket", which is not used by ATP. It displaces the
Asp168-Phe169-Gly170 motif at the start of the activation loop, promoting a
"DFG-out" conformation. Some other inhibitors bind only in the purine site, with
p38alpha remaining in a "DFG-in" conformation. We now demonstrate that
selectivity pocket compounds prevent MKK6-dependent activation of p38alpha in
addition to inhibiting catalysis by activated p38alpha. Inhibitors using only
the purine site do not prevent MKK6-dependent activation. We present kinetic
analyses of seven inhibitors, whose crystal structures as complexes with
p38alpha have been determined. This work includes four new crystal structures
and a novel assay to measure K(d) for nonactivated p38alpha. Selectivity pocket
compounds associate with p38alpha over 30-fold more slowly than purine site
compounds, apparently due to low abundance of the DFG-out conformation. At
concentrations that inhibit cellular production of an inflammatory cytokine,
TNFalpha, selectivity pocket compounds decrease levels of phosphorylated
p38alpha and beta. Stabilization of a DFG-out conformation appears to interfere
with recognition of p38alpha as a substrate by MKK6. ATP competes less
effectively for prevention of activation than for inhibition of catalysis. By
binding to a different conformation of the enzyme, compounds that prevent
activation offer an alternative approach to modulation of p38alpha.
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