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Figure 4.
Figure 4. Insights into interactions with actin via
comparisons with the structure of the Bni1/actin complex. (a)
and (b) The Daam1 FH2 structure is superimposed on the
Bni1/actin complex (PDB ID, 1Y64) in the regions of the knob
actin-binding site (a) and the lasso/post binding site (b). The
actin is colored blue, Daam1 magenta and Bni1 green. Selected
residues that are known to be important for actin assembly by
Bni1 are shown in stick form and labeled. (c) Overall views of
the Daam1 FH2 domain (magenta) superimposed on the Bni1/actin
complex (1Y64). Two actin subunits (yellow and orange) and two
Bni1 FH2 domains (green) from the Bni1/actin structure are
shown; this configuration may represent a “strained”
intermediate in FH2-mediated assembly or actin filaments.^29 The
side-chains of key actin binding residues are shown in CPK form
and are colored red (Ile698 and Lys847 in Daam1; Ile1431 and
Lys1601 in Bni1). The superposition was carried out using the
knob sub-domain only. Note that while the knob and post sites
independently superimpose well on the actin complex ((a) and
(b)), both cannot be simultaneously brought into register with
actin due to a different relative orientation of the knob
sub-domain. Bringing the knob into register (side view) leaves
the actin binding residues in the lasso/post region displaced
from actin by  vert,
similar 17 Å (best seen in the top view).
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