 |
PDBsum entry 2vm2
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Oxidoreductase
|
PDB id
|
|
|
|
2vm2
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
References listed in PDB file
|
|
|
Key reference
|
|
|
Title
|
|
Crystal structures of barley thioredoxin h isoforms hvtrxh1 and hvtrxh2 reveal features involved in protein recognition and possibly in discriminating the isoform specificity.
|
|
|
Authors
|
|
K.Maeda,
P.Hägglund,
C.Finnie,
B.Svensson,
A.Henriksen.
|
|
|
Ref.
|
|
Protein Sci, 2008,
17,
1015-1024.
[DOI no: ]
|
|
|
PubMed id
|
|
|
|
|
|
|
|
|
Abstract
|
|
|
H-type thioredoxins (Trxs) constitute a particularly large Trx sub-group in
higher plants. Here, the crystal structures are determined for the two barley
Trx h isoforms, HvTrxh1 and HvTrxh2, in the partially radiation-reduced state to
resolutions of 1.7 A, and for HvTrxh2 in the oxidized state to 2.0 A. The two
Trxs have a sequence identity of 51% and highly similar fold and active-site
architecture. Interestingly, the four independent molecules in the crystals of
HvTrxh1 form two relatively large and essentially identical protein-protein
interfaces. In each interface, a loop segment of one HvTrxh1 molecule is
positioned along a shallow hydrophobic groove at the primary nucleophile Cys40
of another HvTrxh1 molecule. The association mode can serve as a model for the
target protein recognition by Trx, as it brings the Met82 Cgamma atom (gamma
position as a disulfide sulfur) of the bound loop segment in the proximity of
the Cys40 thiol. The interaction involves three characteristic backbone-backbone
hydrogen bonds in an antiparallel beta-sheet-like arrangement, similar to the
arrangement observed in the structure of an engineered, covalently bound complex
between Trx and a substrate protein, as reported by Maeda et al. in an earlier
paper. The occurrence of an intermolecular salt bridge between Glu80 of the
bound loop segment and Arg101 near the hydrophobic groove suggests that charge
complementarity plays a role in the specificity of Trx. In HvTrxh2, isoleucine
corresponds to this arginine, which emphasizes the potential for specificity
differences between the coexisting barley Trx isoforms.
|
|
|
|
|
|
|
|
Figure 2.
Figure 2. Active-site architecture of HvTrxh1 (A) and
HvTrxh2 (B). Carbon, nitrogen, oxygen, and sulfur atoms are
colored green, blue, red, and yellow, respectively. The 2F
[o]–F [c] electron density maps are presented as a gray
isosurface mesh at the 1.0  level. The
water molecule buried in the internal cavity is shown as a
sphere and is modeled in two alternative positions in HvTrxh1.
For the HvTrxh2 structure, Cys46 and Cys49 are shown only in the
reduced conformations, although they are also modeled in the
oxidized conformations.
|
|
Figure 3.
Figure 3. Radiation disruption of the active-site disulfide
in HvTrxh2. Stereo images of HvTrxh2[OX] (A) and HvTrxh2[RED2],
80% reduced (B), showing a close-up view of segment
Cys46–Cys49. The 2F [o]–F [c] electron density maps are
shown as gray isosurface mesh at the 1.0 level. (C)
HvTrxh2[RED1] with the 1/V  | F(h)[RED1]
– F(h)[RED2] | e^i ^ RED2(h) e ^–2
 i(h – r)
difference electron density contoured at the 7 level.
Significant negative (red) density represents areas where the
HvTrxh2[RED2] structure has a higher level of electron density
than the HvTrxh2[RED1] structure, and positive (green) electron
density, the opposite. For HvTrxh2[RED1] and HvTrxh2[RED2]
structures, Cys46 and Cys49 are modeled and shown in two
alternative conformations (for oxidized and reduced states).
|
|
|
|
|
|
The above figures are
reprinted
by permission from the Protein Society:
Protein Sci
(2008,
17,
1015-1024)
copyright 2008.
|
|
|
|
|
|
|
