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PDBsum entry 1hvq
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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 structures of hevamine, A plant defence protein with chitinase and lysozyme activity, And its complex with an inhibitor.
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Authors
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A.C.Terwisscha van scheltinga,
K.H.Kalk,
J.J.Beintema,
B.W.Dijkstra.
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Ref.
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Structure, 1994,
2,
1181-1189.
[DOI no: ]
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PubMed id
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Abstract
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BACKGROUND: Hevamine is a member of one of several families of plant chitinases
and lysozymes that are important for plant defence against pathogenic bacteria
and fungi. The enzyme can hydrolyze the linear polysaccharide chains of chitin
and peptidoglycan. A full understanding of the structure/function relationships
of chitinases might facilitate the production of transgenic plants with
increased resistance towards a wide range of pathogens. RESULTS: The crystal
structure of hevamine has been determined to a resolution of 2.2 A, and refined
to an R-factor of 0.169. The enzyme possesses a (beta alpha)8-barrel fold. An
inhibitor binding study shows that the substrate-binding cleft is located at the
carboxy-terminal end of the beta-barrel, near the conserved Glu127. Glu127 is in
a position to act as the catalytic proton donor, but no residue that might
stabilize a positively charged oxocarbonium ion intermediate was found. A likely
mechanism of substrate hydrolysis is by direct attack of a water molecule on the
C1 atom of the scissile bond, resulting in inversion of the configuration at C1.
CONCLUSIONS: The structure of hevamine shows a completely new lysozyme/chitinase
fold and represents a new class of polysaccharide-hydrolyzing (beta
alpha)8-barrel enzymes. Because the residues conserved in the family to which
hevamine belongs are important for maintaining the structure of the (beta
alpha)8-barrel, all members of the family, including fungal, bacterial and
insect chitinases, are likely to share this architecture. The crystal structure
obtained provides a basis for protein engineering studies in this family of
chitinases.
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Figure 4.
Figure 4. Schematic drawing of the hydrogen-bonding pattern of
the consensus regions. The highly conserved side chains and the
hydrogen bonds that they make within the consensus regions are
shown in red, the rest of the consensus regions are shown in
blue. Hydrogen bonds made with residues outside the consensus
regions are shown in green. Protonation of the side chains is
shown to be most probable at pH 4.0, the pH optimum of hevamine.
Figure 4. Schematic drawing of the hydrogen-bonding pattern
of the consensus regions. The highly conserved side chains and
the hydrogen bonds that they make within the consensus regions
are shown in red, the rest of the consensus regions are shown in
blue. Hydrogen bonds made with residues outside the consensus
regions are shown in green. Protonation of the side chains is
shown to be most probable at pH 4.0, the pH optimum of hevamine.
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Figure 6.
Figure 6. Stereo figure showing the van der Waals interactions
between hevamine and tri-NAG. Figure 6. Stereo figure showing
the van der Waals interactions between hevamine and tri-NAG.
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The above figures are
reprinted
by permission from Cell Press:
Structure
(1994,
2,
1181-1189)
copyright 1994.
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Secondary reference #1
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Title
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Crystallization of hevamine, An enzyme with lysozyme/chitinase activity from hevea brasiliensis latex.
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Authors
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H.J.Rozeboom,
A.Budiani,
J.J.Beintema,
B.W.Dijkstra.
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Ref.
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J Mol Biol, 1990,
212,
441-443.
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PubMed id
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