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PDBsum entry 1b8g
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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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Structure of 1-Aminocyclopropane-1-Carboxylate synthase, A key enzyme in the biosynthesis of the plant hormone ethylene.
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Authors
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G.Capitani,
E.Hohenester,
L.Feng,
P.Storici,
J.F.Kirsch,
J.N.Jansonius.
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Ref.
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J Mol Biol, 1999,
294,
745-756.
[DOI no: ]
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PubMed id
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Abstract
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The 2.4 A crystal structure of the vitamin B6-dependent enzyme
1-aminocyclopropane-1-carboxylate (ACC) synthase is described. This enzyme
catalyses the committed step in the biosynthesis of ethylene, a plant hormone
that is responsible for the initiation of fruit ripening and for regulating many
other developmental processes. ACC synthase has 15 % sequence identity with the
well-studied aspartate aminotransferase, and a completely different catalytic
activity yet the overall folds and the active sites are very similar. The new
structure together with available biochemical data enables a comparative
mechanistic analysis that largely explains the catalytic roles of the conserved
and non-conserved active site residues. An external aldimine reaction
intermediate (external aldimine with ACC, i.e. with the product) has been
modeled. The new structure provides a basis for the rational design of
inhibitors with broad agricultural applications.
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Figure 3.
Figure 3. Active site views of ACC synthase. (a) Stereo view of the ACC synthase active site with the most import-
ant residues labeled (prepared with the program O (Jones & Kjeldgaard, 1991)). Residues within a sphere of 11 Å of
the cofactor are depicted in yellow and atom colors, and shown in each two alternative conformation. Tyr85, which
is contributed by the neighboring subunit, is labeled with an asterisk. (b) Detailed stereo view of the ACC synthase
active site (subunit B), showing the covalent linkage between the cofactor and Lys273. The final 2Fo
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Fc map, con-
toured at 1.2s, is superimposed on the atomic model. The model is depicted in yellow and atom colors. The unde-
fined additional density in front of the cofactor and modeled as three water molecules (red spheres) is visible at the
top right. Prepared with O.
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Figure 4.
Figure 4. Stereo view of the superposition of the ACC synthase and AATase active sites. Residues within 11 Å of
the cofactors are shown. ACC synthase is depicted in yellow, AATase in green. Residue labels for ACC synthase
appear in gold, those for AATase residues in black. Tyr85 (ACC synthase) and Tyr70 and Arg292 (AATase) are con-
tributed by the neighboring subunit and are labeled with an asterisk. Prepared with O.
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The above figures are
reprinted
by permission from Elsevier:
J Mol Biol
(1999,
294,
745-756)
copyright 1999.
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