 |
PDBsum entry 1a4f
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Oxygen transport
|
PDB id
|
|
|
|
1a4f
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
 |
Contents |
 |
|
|
|
|
|
|
|
|
|
|
|
|
* Residue conservation analysis
|
|
|
|
|
References listed in PDB file
|
|
|
Key reference
|
|
|
Title
|
|
The crystal structure of a high oxygen affinity species of haemoglobin (bar-Headed goose haemoglobin in the oxy form).
|
|
|
Authors
|
|
J.Zhang,
Z.Hua,
J.R.Tame,
G.Lu,
R.Zhang,
X.Gu.
|
|
|
Ref.
|
|
J Mol Biol, 1996,
255,
484-493.
[DOI no: ]
|
|
|
PubMed id
|
|
|
|
|
|
Abstract
|
|
|
We have determined the crystal structure of bar-headed goose haemoglobin in the
oxy form to a resolution of 2.0 A. The R-factor of the model is 19.8%. The
structure is similar to human HbA, but contacts between the subunits show
slightly altered packing of the tetramer. Bar-headed goose blood shows a greatly
elevated oxygen affinity compared to closely related species of geese. This is
apparently due to a single proline to alanine mutation at the alpha 1 beta 1
interface which destabilises the T state of the protein. The beta chain N and C
termini are well-localized, and together with other neighbouring basic groups
they form a strongly positively charged groove at the entrance to the central
cavity around the molecular dyad. The well-ordered conformation and the
three-dimensional distribution of positive charges clearly indicate this area to
be the inositol pentaphosphate binding site of bird haemoglobins.
|
|
|
|
|
|
|
|
Figure 4.
Figure 4. Electron density over Ala a119 and Leu b55, contoured at 1s. The position of the ring of proline a119 of
human Hb superimposed on the goose structure is shown in broken lines.
|
|
Figure 5.
Figure 5. Ramachandran plot for bar-headed goose Hb, drawn with PROCHECK (Laskowski et al., 1993). Glycine
residues are shown as triangles. Two residues have unusual fc angles, Ala b119 and Leu a2. The N-terminal region
of the a chain could not be readily fitted into the density and the temperature factors of atoms in the first five residues
are high, indicating some disorder. In contrast, Ala b119 is well ordered and the C
b
and carbonyl oxygen atoms can
be clearly observed in the electron density map. This residue adopts a similar conformation to the glycine found in
most vertebrate haemoglobins at this position at the GH corner.
|
|
|
|
|
|
The above figures are
reprinted
by permission from Elsevier:
J Mol Biol
(1996,
255,
484-493)
copyright 1996.
|
|
|
|
|
|
|
