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PDBsum entry 2ax2
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References listed in PDB file
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Key reference
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Title
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Production and X-Ray crystallographic analysis of fully deuterated human carbonic anhydrase ii.
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Authors
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M.Budayova-Spano,
S.Z.Fisher,
M.T.Dauvergne,
M.Agbandje-Mckenna,
D.N.Silverman,
D.A.Myles,
R.Mckenna.
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Ref.
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Acta Crystallogr Sect F Struct Biol Cryst Commun, 2006,
62,
6-9.
[DOI no: ]
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PubMed id
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Abstract
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Human carbonic anhydrase II (HCA II) is a zinc metalloenzyme that catalyzes the
reversible hydration and dehydration of carbon dioxide and bicarbonate,
respectively. The rate-limiting step in catalysis is the intramolecular transfer
of a proton between the zinc-bound solvent (H2O/OH-) and the proton-shuttling
residue His64. This distance (approximately 7.5 A) is spanned by a well defined
active-site solvent network stabilized by amino-acid side chains (Tyr7, Asn62,
Asn67, Thr199 and Thr200). Despite the availability of high-resolution
(approximately 1.0 A) X-ray crystal structures of HCA II, there is currently no
definitive information available on the positions and orientations of the H
atoms of the solvent network or active-site amino acids and their ionization
states. In preparation for neutron diffraction studies to elucidate this
hydrogen-bonding network, perdeuterated HCA II has been expressed, purified,
crystallized and its X-ray structure determined to 1.5 A resolution. The refined
structure is highly isomorphous with hydrogenated HCA II, especially with regard
to the active-site architecture and solvent network. This work demonstrates the
suitability of these crystals for neutron macromolecular crystallography.
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Figure 1.
Active site of (a) hydrogenated and (b) perdeuterated HCA II.
Important catalytic side chains in the active sites are shown in
yellow ball-and-stick representation and are as labeled. The Zn
atom is shown as a black sphere, while solvent molecules are in
red. Inferred hydrogen bonds are shown as orange dashed lines.
(a) Hydrogenated HCA II (PDB code 1tbt; Fisher et al.,
2005[triangle]) and (b) perdeuterated HCA II; the blue electron
density shown is a 2F [o] [minus sign] F [c] map contoured at
1.5[sigma]. The figure was generated and rendered using
MOLSCRIPT and RASTER3D (Esnouf, 1999[triangle]; Merritt & Bacon,
1997[triangle]). Acta Crystallogr Sect F Struct Biol Cryst
Commun. 2006 January 1; 62(Pt 1): 6–9. Published online 2005
December 16. doi: 10.1107/S1744309105038248. Copyright
[copyright] International Union of Crystallography 2006
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Figure 2.
Optical photograph of a perdeuterated HCA II crystal of
approximate dimensions 0.4 x 0.4 x 0.1 mm. Acta Crystallogr Sect
F Struct Biol Cryst Commun. 2006 January 1; 62(Pt 1): 6–9.
Published online 2005 December 16. doi:
10.1107/S1744309105038248. Copyright [copyright] International
Union of Crystallography 2006
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The above figures are
reprinted
from an Open Access publication published by the IUCr:
Acta Crystallogr Sect F Struct Biol Cryst Commun
(2006,
62,
6-9)
copyright 2006.
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