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PDBsum entry 1pju
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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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Unbound form of tomato inhibitor-Ii reveals interdomain flexibility and conformational variability in the reactive site loops.
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Authors
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I.H.Barrette-Ng,
K.K.Ng,
M.M.Cherney,
G.Pearce,
U.Ghani,
C.A.Ryan,
M.N.James.
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Ref.
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J Biol Chem, 2003,
278,
31391-31400.
[DOI no: ]
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PubMed id
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Abstract
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The Potato II (Pot II) family of proteinase inhibitors plays important roles in
the constitutive and inducible defense of plants against predation by a wide
range of pests. The structural basis of inhibition by a multidomain Pot II
family inhibitor was revealed recently by the structure of the ternary complex
between the two-headed tomato inhibitor-II (TI-II) and two molecules of
subtilisin Carlsberg. Here we report the 2.15-A resolution crystal structure of
the unbound form of TI-II that reveals significant conformational flexibility in
the absence of bound proteinase molecules. The four independent copies of
unbound TI-II in the asymmetric unit of the unit cell display a range of
different conformations when compared with the bound form of the inhibitor, most
strikingly in the orientations of the inhibitory domains and in the
conformations of the reactive site loops. One of the two linker segments
(residues 74 to 79) between the two domains as well as the adjacent beta-strand
in Domain I (residues 80-85) is well ordered in all four copies of the unbound
inhibitor, even though this region appeared to be disordered in the structure of
the ternary complex. Conformational flexibility seen in the reactive site loops
of unbound TI-II suggests a mechanism by which the inhibitor can balance the
need for tight binding with the need for broad inhibitory function.
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Figure 2.
FIG. 2. Conformational change in linker region of unbound
TI-II. A stereoscopic view of linker residues 15-18 (shown in
magenta) and residues 76-80 (shown in black) of copy A (A) and
copy B (B) is shown. Omit map electron density corresponding to
Arg-17 has been contoured at 3.4  .
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Figure 3.
FIG. 3. Least-squares superpositions of unbound TI-II onto
bound TI-II. A stereoscopic view of a least-squares
superposition of copies A and B (A) and copies C and D (B) onto
the structure of TI-II from the TI-II:(subtilisin)[2] complex is
shown. The bound form of TI-II is drawn in magenta, whereas the
unbound forms are shown in red in Domain I and blue in Domain II.
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2003,
278,
31391-31400)
copyright 2003.
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