 |
PDBsum entry 1dk0
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Transport protein
|
PDB id
|
|
|
|
1dk0
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
 |
Contents |
 |
|
|
|
|
|
|
|
|
|
|
|
|
* Residue conservation analysis
|
|
|
|
|
References listed in PDB file
|
|
|
Key reference
|
|
|
Title
|
|
Functional aspects of the heme bound hemophore hasa by structural analysis of various crystal forms.
|
|
|
Authors
|
|
P.Arnoux,
R.Haser,
N.Izadi-Pruneyre,
A.Lecroisey,
M.Czjzek.
|
|
|
Ref.
|
|
Proteins, 2000,
41,
202-210.
[DOI no: ]
|
|
|
PubMed id
|
|
|
|
|
|
Abstract
|
|
|
The protein HasA from the Gram negative bacteria Serratia marcescens is the
first hemophore to be described at the molecular level. It participates to the
shuttling of heme from hemoglobin to the outer membrane receptor HasR, which in
turn releases it into the bacterium. HasR alone is also able to take up heme
from hemoglobin but synergy with HasA increases the efficiency of the system by
a factor of about 100. This iron acquisition system allows the bacteria to
survive with hemoglobin as the sole iron source. Here we report the structures
of a new crystal form of HasA diffracting up to 1.77A resolution as well as the
refined structure of the trigonal crystal form diffracting to 3.2A resolution.
The crystal structure of HasA at high resolution shows two possible orientations
of the heme within the heme-binding pocket, which probably are functionally
involved in the heme-iron acquisition process. The detailed analysis of the
three known structures reveals the molecular basis regulating the relative
affinity of the heme/hemophore complex.
|
|
|
|
|
|
|
|
Figure 3.
Figure 3. Illustration of the two possibilities of inserting
the heme into the protein moiety assessed by high resolution
X-ray crystallography: A: electron density maps: 3F[o]-2F[c] map
contoured at 1  (blue)
and F[o]-F[c] map contoured at -2.5 (red)
and +2.5 (green),
B: the corresponding two orientations of the heme.
|
|
Figure 4.
Figure 4. Schematic representation of the heme environment. In
the hemophore structure the most exposed heme edge is on side b
(side defined in Fig. 5). Each propionate is involved in several
hydrogen bonds with the protein, in this way forming a  propionate
zip.
|
|
|
|
|
|
The above figures are
reprinted
by permission from John Wiley & Sons, Inc.:
Proteins
(2000,
41,
202-210)
copyright 2000.
|
|
|
Secondary reference #1
|
|
|
Title
|
|
The crystal structure of hasa, A hemophore secreted by serratia marcescens.
|
|
|
Authors
|
|
P.Arnoux,
R.Haser,
N.Izadi,
A.Lecroisey,
M.Delepierre,
C.Wandersman,
M.Czjzek.
|
|
|
Ref.
|
|
Nat Struct Biol, 1999,
6,
516-520.
[DOI no: ]
|
|
|
PubMed id
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Figure 2.
Figure 2. Backbone structure of HasA. a, Ribbon diagram with
helices colored in red and strands in blue. The ligands of the
heme and the heme are shown in ball-and-stick representation.
The surface occupied by the heme is transparent. b, Same
representation as (a) but rotated by 90°. The figures have
been computed using MOLSCRIPT^32, GRASP^33 and Raster3D^34.
|
|
Figure 4.
Figure 4. View of the residues in the heme binding site. His
83 is presumed to be involved in both processes of heme capture
and release. The residues and the heme are shown in
ball-and-stick representation. The surrounding backbone is
represented as a ribbon.
|
|
|
|
|
|
The above figures are
reproduced from the cited reference
with permission from Macmillan Publishers Ltd
|
|
|
|
|
|
|
