 |
PDBsum entry 1mdu
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Structural protein
|
PDB id
|
|
|
|
1mdu
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
 |
Contents |
 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
* Residue conservation analysis
|
|
|
|
|
References listed in PDB file
|
|
|
Key reference
|
|
|
Title
|
|
Structure of an f-Actin trimer disrupted by gelsolin and implications for the mechanism of severing.
|
|
|
Authors
|
|
J.F.Dawson,
E.P.Sablin,
J.A.Spudich,
R.J.Fletterick.
|
|
|
Ref.
|
|
J Biol Chem, 2003,
278,
1229-1238.
[DOI no: ]
|
|
|
PubMed id
|
|
|
|
|
|
Abstract
|
|
|
Stable oligomers of filamentous actin were obtained by cross-linking F-actin
with 1,4-N,N'-phenylenedimaleimide and depolymerization with excess segment-1 of
gelsolin. Segment-1-bound and cross-linked actin oligomers containing either two
or three actin subunits were purified and shown to nucleate actin assembly.
Kinetic assembly data from mixtures of monomeric actin and the actin oligomers
fit a nucleation model where cross-linked actin dimer or trimer reacts with an
actin monomer to produce a competent nucleus for filament assembly. We report
the three-dimensional structure of the segment-1-actin hexamer containing three
actin subunits, each with a tightly bound ATP. Comparative analysis of this
structure with twelve other actin structures provides an atomic level
explanation for the preferential binding of ATP by the segment-1-complexed
actin. Although the structure of segment-1-bound actin trimer is topologically
similar to the helical model of F-actin (1), it has a distorted symmetry
compared with that of the helical model. This distortion results from
intercalation of segment-1 between actin protomers that increase the rise per
subunit and rotate each of the actin subunits relative to their positions in
F-actin. We also show that segment-1 of gelsolin is able to sever actin
filaments, although the severing activity of segment-1 is significantly lower
than full-length gelsolin.
|
|
|
|
|
|
|
|
Figure 4.
Fig. 4. Structure of the GS-1-complexed actin trimer.
Actin subunits in the trimer complex are colored in dark green,
orange, and blue. The corresponding segments of gelsolin are
light green, yellow, and cyan. The structure of each GS-1-bound
protomer in the trimer is similar to the structures of
GS-1-complexed actin solved previously. In each protomer, the
bound nucleotide, Ca^2+-ATP, is shown as a gray space-filling
model. Coordinated ions of Ca^2+ are drawn as red spheres. The
pPDM cross-link is between Lys-193 of one actin subunit and
Cys-376 of its neighbor. In each actin subunit, the C-terminal
residues 375-377 and residues corresponding to DNase I binding
loop are disordered and are not included in the model. The
dashed lines, therefore, connect the cross-linked Lys-193 of
subunits 1 and 2 to the last visible C-terminal residue,
Arg-374, of subunits 2 and 3, respectively.
|
|
Figure 6.
Fig. 6. Comparative analysis of the intersubunit contacts
in the X-actin and F-actin filaments. A, structural elements
forming the interface in the X-actin. Amino acid residues
197-199 (yellow), 225-238 (red), and 253-258 (orange) from an
actin subunit N and residues 112-116 (light green), 174-180
(dark green), 271-274 (blue), and 285-289 (cyan) from an
adjacent subunit N+1 are highlighted, and their positions are
indicated in the F-actin filament (B). Magnified view of the
structural elements buried at the X-actin interface (C) and
their positions at the interface of the F-actin (D) are shown.
Coloring scheme is consistent for all panels.
|
|
|
|
|
|
The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2003,
278,
1229-1238)
copyright 2003.
|
|
|
|
|
|
|
