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PDBsum entry 1fiz
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Contents |
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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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Effector sites in the three-Dimensional structure of mammalian sperm beta-Acrosin.
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Authors
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R.Tranter,
J.A.Read,
R.Jones,
R.L.Brady.
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Ref.
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Structure, 2000,
8,
1179-1188.
[DOI no: ]
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PubMed id
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Abstract
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BACKGROUND: Proacrosin is a serine protease found specifically within the
acrosomal vesicle of all mammalian spermatozoa. During fertilization proacrosin
autoactivates to form beta-acrosin, in which there is a "light" chain
cross-linked to a "heavy" chain by two disulphide bonds. beta-acrosin
is thought to be multifunctional with roles in acrosomal exocytosis, as a
receptor for zona pellucida proteins, and as a protease to facilitate
penetration of spermatozoa into the egg. RESULTS: The crystal structures of both
ram and boar beta-acrosins have been solved in complex with p-aminobenzamidine
to 2.1 A and 2.9 A resolution, respectively. Both enzymes comprise a heavy chain
with structural homology to trypsin, and a light chain covalently associated in
a similar manner to blood coagulation enzymes. In crystals of boar beta-acrosin,
the carboxyl terminus of the heavy chain is inserted into the active site of the
neighboring molecule. In both enzyme structures, there are distinctive
positively charged surface "patches" close to the active site, which
associate with carbohydrate from adjacent molecules and also bind sulfate ions.
CONCLUSIONS: From the three-dimensional structure of beta-acrosin, two separate
effector sites are evident. First, proteolytic activity, believed to be
important at various stages during fertilization, arises from the trypsin-like
active site. Activity of this site may be autoregulated through intermolecular
associations. Second, positively charged regions on the surface adjacent to the
active site may act as receptors for binding zona pellucida glycoproteins. The
spatial proximity of these two effector sites suggests there may be synergy
between them.
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Figure 4.
Figure 4. Active Site of Boar b-Acrosin(a) The boar
b-acrosin heavy chain carboxyl terminus inserts into the active
site of a neighboring molecule. The figure shows the placement
of the heavy chain carboxyl terminus (residues Pro-255, Pro-256,
and Arg-257) and adjacent loop residues Asp-201, Arg-202, and
Ala-203 within the active site of another molecule (shown as a
molecular surface). The location of the catalytic site serine
(Ser-195) is marked by the pink surface, the p-aminobenzamidine
inhibitor is shown in green, and the specificity pockets are
labeled according to the convention of [24].(b) Corresponding
electron density (2|F[obs]| - |F[calc]| coefficients contoured
at 1 s) for the active site region shown in part (a). Density
for the residues inserted into the active site are shown, along
with the density corresponding to the active site serine
(Ser-195) and the p-aminobenzamidine inhibitor
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The above figure is
reprinted
by permission from Cell Press:
Structure
(2000,
8,
1179-1188)
copyright 2000.
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Secondary reference #1
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Title
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Three dimensional structure of beta-Acrosin from ram and boar spermatozoa
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Author
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R.Tranter.
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Ref.
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thesis ...
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