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PDBsum entry 4ajt
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Blood clotting
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PDB id
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4ajt
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References listed in PDB file
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Key reference
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Title
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Structural basis for catalytic activation of protein z-Dependent protease inhibitor (zpi) by protein z.
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Authors
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X.Huang,
Y.Yan,
Y.Tu,
J.Gatti,
G.J.Broze,
A.Zhou,
S.T.Olson.
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Ref.
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Blood, 2012,
120,
1726-1733.
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PubMed id
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Abstract
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The anticoagulant serpin, protein Z-dependent protease inhibitor (ZPI), is
catalytically activated by its cofactor, protein Z (PZ), to regulate the
function of blood coagulation factor Xa on membrane surfaces. The X-ray
structure of the ZPI-PZ complex has shown that PZ binds to a unique site on ZPI
centered on helix G. In the present study, we show by Ala-scanning mutagenesis
of the ZPI-binding interface, together with native PAGE and kinetic analyses of
PZ binding to ZPI, that Tyr240 and Asp293 of ZPI are crucial hot spots for PZ
binding. Complementary studies with protein Z-protein C chimeras show the
importance of both pseudocatalytic and EGF2 domains of PZ for the critical ZPI
interactions. To understand how PZ acts catalytically, we analyzed the
interaction of reactive loop-cleaved ZPI (cZPI) with PZ and determined the cZPI
X-ray structure. The cZPI structure revealed changes in helices A and G of the
PZ-binding site relative to native ZPI that rationalized an observed 6-fold loss
in PZ affinity and PZ catalytic action. These findings identify the key
determinants of catalytic activation of ZPI by PZ and suggest novel strategies
for ameliorating hemophilic states through drugs that disrupt the ZPI-PZ
interaction.
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