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PDBsum entry 2d3b
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References listed in PDB file
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Key reference
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Title
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Atomic structure of plant glutamine synthetase: a key enzyme for plant productivity.
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Authors
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H.Unno,
T.Uchida,
H.Sugawara,
G.Kurisu,
T.Sugiyama,
T.Yamaya,
H.Sakakibara,
T.Hase,
M.Kusunoki.
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Ref.
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J Biol Chem, 2006,
281,
29287-29296.
[DOI no: ]
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PubMed id
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Abstract
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Plants provide nourishment for animals and other heterotrophs as the sole
primary producer in the food chain. Glutamine synthetase (GS), one of the
essential enzymes for plant autotrophy catalyzes the incorporation of ammonia
into glutamate to generate glutamine with concomitant hydrolysis of ATP, and
plays a crucial role in the assimilation and re-assimilation of ammonia derived
from a wide variety of metabolic processes during plant growth and development.
Elucidation of the atomic structure of higher plant GS is important to
understand its detailed reaction mechanism and to obtain further insight into
plant productivity and agronomical utility. Here we report the first crystal
structures of maize (Zea mays L.) GS. The structure reveals a unique decameric
structure that differs significantly from the bacterial GS structure. Higher
plants have several isoenzymes of GS differing in heat stability and catalytic
properties for efficient responses to variation in the environment and
nutrition. A key residue responsible for the heat stability was found to be
Ile-161 in GS1a. The three structures in complex with substrate analogues,
including phosphinothricin, a widely used herbicide, lead us to propose a
mechanism for the transfer of phosphate from ATP to glutamate and to interpret
the inhibitory action of phosphinothricin as a guide for the development of new
potential herbicides.
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Figure 4.
FIGURE 4. Representation of the interactions between enzyme
and substrate analogues. a, stick models for the interaction of
the enzyme with AMPPNP and MetSox. Carbon, oxygen, nitrogen,
phosphorus, and sulfur atoms are colored gray, red, blue,
salmon, and yellow, respectively. Three Mn^2+ are indicated in
pink spheres. Dotted lines designate hydrogen bonds and
coordination bonds to Mn^2+ ions. Residues without dotted lines
have hydrophobic interactions with the substrate. b, stick
models for the interaction of the enzyme with ADP and MetSox. c,
stick models for the interaction of the enzyme with ADP and
PPT-P.
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Figure 7.
FIGURE 7. Active site structure formed by Asp-56 and
Glu-297 of maize GS1a. a, stereo view of the side chain
structures of Asp-56' and Glu-297 together with ADP, MetSox-P,
and three Mn^2+ ions. b, alignments of short stretches of amino
acid sequences containing Asp-56 and Glu-297 in GSs from M.
tuberculosis (MtGS), S. typhimurium (StGS), maize (GS1 isozymes
GS1a, GS1d, andGS2), Arabidopsis, human, and chicken.
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2006,
281,
29287-29296)
copyright 2006.
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