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PDBsum entry 1b8v
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Oxidoreductase
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PDB id
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1b8v
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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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Structural basis for cold adaptation. Sequence, Biochemical properties, And crystal structure of malate dehydrogenase from a psychrophile aquaspirillium arcticum.
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Authors
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S.Y.Kim,
K.Y.Hwang,
S.H.Kim,
H.C.Sung,
Y.S.Han,
Y.Cho.
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Ref.
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J Biol Chem, 1999,
274,
11761-11767.
[DOI no: ]
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PubMed id
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Abstract
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Aquaspillium arcticum is a psychrophilic bacterium that was isolated from arctic
sediment and grows optimally at 4 degrees C. We have cloned, purified, and
characterized malate dehydrogenase from A. arcticum (Aa MDH). We also have
determined the crystal structures of apo-Aa MDH, Aa MDH.NADH binary complex, and
Aa MDH.NAD.oxaloacetate ternary complex at 1.9-, 2.1-, and 2.5-A resolutions,
respectively. The Aa MDH sequence is most closely related to the sequence of a
thermophilic MDH from Thermus flavus (Tf MDH), showing 61% sequence identity and
over 90% sequence similarity. Stability studies show that Aa MDH has a half-life
of 10 min at 55 degrees C, whereas Tf MDH is fully active at 90 degrees C for 1
h. Aa MDH shows 2-3-fold higher catalytic efficiency compared with a mesophilic
or a thermophilic MDH at the temperature range 4-10 degrees C. Structural
comparison of Aa MDH and Tf MDH suggests that the increased relative flexibility
of active site residues, favorable surface charge distribution for substrate and
cofactor, and the reduced intersubunit ion pair interactions may be the major
factors for the efficient catalytic activity of Aa MDH at low temperatures.
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Figure 2.
Fig. 2. a, a simulated annealed omit map around the NADH
in Aa MDH·NADH complex. The map is shown with a contour
level of 1  . b, a
stereodiagram of the NADH binding site in Aa MDH. Important
residues interacting with NADH are labeled, and distances
between them are shown.
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Figure 3.
Fig. 3. a, an omit map around the oxaloacetate in the Aa
MDH ternary complex. The map is shown with a contour level of 1
. b, a
stereodiagram of the oxaloacetate binding site in Aa MDH.
Important residues interacting with oxaloacetate are labeled,
and distances between them are shown.
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(1999,
274,
11761-11767)
copyright 1999.
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