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PDBsum entry 4roa
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Hydrolase inhibitor
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PDB id
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4roa
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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 and inhibitory effects of hinge loop mutagenesis in serpin-2 from the malaria vector anopheles gambiae.
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Authors
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X.Zhang,
D.A.Meekins,
C.An,
M.Zolkiewski,
K.P.Battaile,
M.R.Kanost,
S.Lovell,
K.Michel.
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Ref.
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J Biol Chem, 2015,
290,
2946-2956.
[DOI no: ]
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PubMed id
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Note: In the PDB file this reference is
annotated as "TO BE PUBLISHED". The citation details given above have
been manually determined.
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Abstract
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Serpin-2 (SRPN2) is a key negative regulator of the melanization response in the
malaria vector Anopheles gambiae. SRPN2 irreversibly inhibits clip domain serine
proteinase 9 (CLIPB9), which functions in a serine proteinase cascade
culminating in the activation of prophenoloxidase and melanization. Silencing of
SRPN2 in A. gambiae results in spontaneous melanization and decreased life span
and is therefore a promising target for vector control. The previously
determined structure of SRPN2 revealed a partial insertion of the hinge region
of the reactive center loop (RCL) into β sheet A. This partial hinge insertion
participates in heparin-linked activation in other serpins, notably antithrombin
III. SRPN2 does not contain a heparin binding site, and any possible mechanistic
function of the hinge insertion was previously unknown. To investigate the
function of the SRPN2 hinge insertion, we developed three SRPN2 variants in
which the hinge regions are either constitutively expelled or inserted and
analyzed their structure, thermostability, and inhibitory activity. We
determined that constitutive hinge expulsion resulted in a 2.7-fold increase in
the rate of CLIPB9Xa inhibition, which is significantly lower than previous
observations of allosteric serpin activation. Furthermore, we determined that
stable insertion of the hinge region did not appreciably decrease the
accessibility of the RCL to CLIPB9. Together, these results indicate that the
partial hinge insertion in SRPN2 does not participate in the allosteric
activation observed in other serpins and instead represents a molecular
trade-off between RCL accessibility and efficient formation of an inhibitory
complex with the cognate proteinase.
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