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PDBsum entry 1v3w
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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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Observation of a calcium-Binding site in the gamma-Class carbonic anhydrase from pyrococcus horikoshii.
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Authors
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J.Jeyakanthan,
S.Rangarajan,
P.Mridula,
S.P.Kanaujia,
Y.Shiro,
S.Kuramitsu,
S.Yokoyama,
K.Sekar.
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Ref.
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Acta Crystallogr D Biol Crystallogr, 2008,
64,
1012-1019.
[DOI no: ]
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PubMed id
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Abstract
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Carbonic anhydrases are zinc-containing metalloenzymes that catalyze the
interconversion of carbon dioxide and bicarbonate. Three crystal structures of
gamma-class carbonic anhydrase (one of which is bound to a bicarbonate molecule)
from the aerobic OT3 strain of the hyperthermophilic archeon Pyrococcus
horikoshii have been solved by molecular replacement in space group F4(1)32. The
asymmetric unit contains a monomer of 173 amino acids and a catalytic Zn2+ ion.
The protein fold is a regular prism formed by a left-handed beta-helix, similar
to previously reported structures. The active-site Zn2+ ion located at the
interface between the two monomers is bound to three histidyl residues and a
water molecule in a tetrahedral fashion. In addition to the 20 beta-strands
comprising the beta-helix, there is also a long C-terminal alpha-helix. For the
first time, Ca2+ ions have been observed in addition to the catalytic Zn2+ ion.
It is hypothesized that Tyr159 (which corresponds to the catalytically important
Asn202 in previously reported structures) utilizes C-H...pi interactions to
fulfill its functions. This study may shed light on the catalytic mechanism of
the enzyme and throw open new questions on the mechanism of product removal in
carbonic anhydrases.
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Figure 3.
Figure 3 In this representation of the Zn-Cap trimer (generated
from 1v67 ), metal ions are shown as spheres. The central Ca^2+
ion is in magenta, the Zn^2+ ions in brick red and the positions
of the Cl^- ions from a 1v3w trimer are shown as green circles.
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Figure 4.
Figure 4 Metal-ion coordination. (a) Zn^2+ is coordinated to
His65A ND1, His87A NE2, His82B NE2, HOH44 and Tyr159B OH. The OH
is at a distance of 2.71 Å from Zn^2+. (b) The Ca^2+ ion
is coordinated to Ser40 OG and Asn61 OD1 from all three chains.
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The above figures are
reprinted
by permission from the IUCr:
Acta Crystallogr D Biol Crystallogr
(2008,
64,
1012-1019)
copyright 2008.
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