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PDBsum entry 1v9e
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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 bovine carbonic anhydrase ii at 1.95 a resolution.
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Authors
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R.Saito,
T.Sato,
A.Ikai,
N.Tanaka.
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Ref.
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Acta Crystallogr D Biol Crystallogr, 2004,
60,
792-795.
[DOI no: ]
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PubMed id
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Abstract
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Carbonic anhydrase (CA) is a zinc-containing enzyme that catalyzes the
reversible hydration of CO2 to HCO3-. In eukaryotes, the enzyme plays a role in
various physiological functions, including interconversion between CO2 and HCO3-
in intermediary metabolism, facilitated diffusion of CO2, pH homeostasis and ion
transport. The structure of bovine carbonic anhydrase II (BCA II) has been
determined by molecular replacement and refined to 1.95 A resolution by
simulated-annealing and individual B-factor refinement. The final R factor for
the BCA II structure was 19.4%. BCA II has a C-terminal knot structure similar
to that observed in human CA II. It contains one zinc ion in the active site
coordinated to three histidines and one putative water molecule in a tetrahedral
geometry. The structure of BCA II reveals a probable alternative proton-wire
pathway that differs from that of HCA II.
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Figure 2.
Figure 2 Schematic drawing of interactions and distances around
the active site determined from the crystal structure of BCA II
at pH 7.5. The net charges assigned by theoretical calculations
using MOPAC are shown. The side-chain atom Gln91 O  1
(net charge -0.30) accepts a hydrogen bond from of His93 N  1
(net charge -0.21) and contributes to His93 ligand
stabilization. The side-chain atom of Gln91 N 2,
with a net charge of -0.40, has a dominant role in the binding
of water molecule W482, with net charge of +0.02, in its
slightly acidic or cationic form. This interaction is likely to
be more hydrogen-bonding in character than the interaction
between W162 (net charge +0.01) and His63 N 2
(net charge -0.14) that has been a biological focus in the case
of HCA II. This finding suggests that the dipole donor group of
Gln91 may also participate in processes that require relatively
rapid proton movement or release.
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The above figure is
reprinted
by permission from the IUCr:
Acta Crystallogr D Biol Crystallogr
(2004,
60,
792-795)
copyright 2004.
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