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PDBsum entry 2aa1
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Oxygen storage/transport
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PDB id
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2aa1
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References listed in PDB file
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Key reference
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Title
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Minimal structural requirements for root effect: crystal structure of the cathodic hemoglobin isolated from the antarctic fish trematomus newnesi.
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Authors
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L.Mazzarella,
G.Bonomi,
M.C.Lubrano,
A.Merlino,
A.Riccio,
A.Vergara,
L.Vitagliano,
C.Verde,
G.Di prisco.
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Ref.
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Proteins, 2006,
62,
316-321.
[DOI no: ]
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PubMed id
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Abstract
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The cathodic hemoglobin component of the Antarctic fish Trematomus newnesi
(HbCTn) is a Root-effect protein. The interpretation of its functional
properties in relation to its sequence is puzzling. Indeed, HbCTn sequence is
characterized by an extremely low histidyl content, and in particular by the
lack of His146beta and His69beta, which are believed to be important in Bohr and
Root effects, respectively. Furthermore, previous analyses suggested that the
local environment of Asp95alpha, Asp99beta, and Asp101beta should not be
appropriate for the formation of Asp-Asp interactions, which are important for
the Root effect. Here, we report the high-resolution crystal structure of the
deoxy form of HbCTn. Our data provide a structural interpretation for the very
low oxygen affinity of the protein and insights into the structural determinants
of the Root effect protein. The structure demonstrates that the presence of
Ile41alpha and Ser97alpha at the alpha1beta2 interface does not prevent the
formation of the inter-Asp interactions in HbCTn, as previous studies had
suggested. The present data indicate that the hydrogen bond formed between
Asp95alpha and Asp101beta, which is stabilized by Asp99beta, is per se
sufficient to generate the Root effect, and it is the minimal structural
requirement needed for the design of Root-effect Hbs.
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Figure 1.
Figure 1. Fo-Fc electron density map of (A) the  heme
region, (B) the C-terminus of -chain,
and (C) the  [1]
[2]
interface at 3.5, 2.5, and 3.5  ,
respectively.
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Figure 2.
Figure 2. Stereo superimposition of the [1]
[2]
interface of the HbTb (black) and HbCTn (gray).
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The above figures are
reprinted
by permission from John Wiley & Sons, Inc.:
Proteins
(2006,
62,
316-321)
copyright 2006.
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Secondary reference #1
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Title
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Crystal structure of trematomus newnesi haemoglobin re-Opens the root effect question.
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Authors
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L.Mazzarella,
R.D'Avino,
G.Di prisco,
C.Savino,
L.Vitagliano,
P.C.Moody,
A.Zagari.
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Ref.
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J Mol Biol, 1999,
287,
897-906.
[DOI no: ]
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PubMed id
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Figure 3.
Figure 3. The F[o]−F[c] electron density omit map of the
βN terminus with superimposed final models of HbTnCO (red) and
HbPbCO (green), showing the different orientation of the βN
terminus. Density is contoured at 2.5σ.
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Figure 4.
Figure 4. The F[o]−F[c] electron density omit map at the
α-haem including the bound histidine residues His59 (E7) and
His88 (F8). Density is contoured at 2.5σ.
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The above figures are
reproduced from the cited reference
with permission from Elsevier
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