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PDBsum entry 2olg
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References listed in PDB file
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Key reference
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Title
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Crystal structure of the serine protease domain of prophenoloxidase activating factor-I.
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Authors
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S.Piao,
S.Kim,
J.H.Kim,
J.W.Park,
B.L.Lee,
N.C.Ha.
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Ref.
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J Biol Chem, 2007,
282,
10783-10791.
[DOI no: ]
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PubMed id
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Abstract
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A family of serine proteases (SPs) mediates the proteolytic cascades of
embryonic development and immune response in invertebrates. These proteases,
called easter-type SPs, consist of clip and chymotrypsin-like SP domains. The SP
domain of easter-type proteases differs from those of typical SPs in its primary
structure. Herein, we report the first crystal structure of the SP domain of
easter-type proteases, presented as that of prophenoloxidase activating factor
(PPAF)-I in zymogen form. This structure reveals several important structural
features including a bound calcium ion, an additional loop with a unique
disulfide linkage, a canyon-like deep active site, and an exposed activation
loop. We subsequently show the role of the bound calcium and the proteolytic
susceptibility of the activation loop, which occurs in a clip domain-independent
manner. Based on biochemical study in the presence of heparin, we suggest that
PPAF-III, highly homologous to PPAF-I, contains a surface patch that is
responsible for enhancing the catalytic activity through interaction with a
nonsubstrate region of a target protein. These results provide insights into an
activation mechanism of easter-type proteases in proteolytic cascades, in
comparison with the well studied blood coagulation enzymes in mammals.
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Figure 2.
Overall structure of the SP domain of PPAF-I, shown in
standard orientation (32). A, a ribbon representation of the
PPAF-I SP domain structure. The SP domain is shown in cyan,
except for several loop regions whose color scheme is as
described in the legend to Fig. 1. Bound calcium ion is in
green, and the three disulfide bonds are drawn with sulfur atoms
in yellow. The catalytic triad residues (Ser-His-Asp) are shown
in the ball-and-stick representation. Asn-131 (c36) in 30-loop
is N-linked glycosylated. B, left, the superimposed Cα traces
of the PPAF-I SP domain (cyan) and chymotrypsinogen (orange; PDB
code 1CGI). Right, the superimposed Cα traces of the PPAF-I SP
domain (cyan) and PPAF-II SP domain (gray; PDB code 2B9L).
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Figure 6.
The canyon-like deep active-site cleft.A, a side view of the
active site from the right of the molecule in Fig. 2A. The
coloring scheme is as in Fig. 2A. The ionic interaction between
Arg-160 and Glu-263 is shown as a dotted line. B, surface
representation of PPAF-I is shown with a Cα worm. The region
and orientation of the molecule are similar to those in Fig. 4A.
The surface representation was generated from a virtual mutant
molecule (R160A/E263A), and it was perpendicularly clipped just
before the catalytic serine residue for clarity. The distance
between Arg-160 and the O-γ of Ser-315 is 11.1 Å as shown.
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2007,
282,
10783-10791)
copyright 2007.
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