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Figure 3.
Figure 3. Metal Ion Rearrangements in β I Domain Activation
(A) Superposition of headpieces from our unliganded-closed
structure and liganded-open α[IIb]β[3] (Springer et al.,
2008). The β I and hybrid domains are yellow (open) and magenta
(closed), while PSI and I-EGF1 domains are red and green,
respectively. The α headpieces are cyan (open) and gray
(closed).
(B) Enlarged view of β I domains with major
differences in yellow (open) and magenta (closed).
(C and
D) β I domain metal coordination sites in unliganded-closed
α[IIb]β[3] (C) and liganded-open α[IIb]β[3] (D). Ca (gold)
and Mg (green) ions are large spheres; waters (red or pink) are
smaller spheres. N atoms are blue and O atoms are red or pink.
Metal coordination and hydrogen bonds are dashed. The loop
bearing M335 moves far away in (D).
(E) Superposition at
the β I MIDAS.
(F) Superposition at the α I MIDAS of
unliganded-closed (PDB code 1LFA) and liganded-open α[L] (PDB
code 1T0P) in the same orientation as the β I MIDAS in (D). In
(C)–(F), carbons for unliganded-closed and liganded-open
integrins and for ligands are wheat, gray, and cyan,
respectively.
(G and H) Electrostatic potential surfaces at
the unliganded (G) and liganded (H) binding sites.
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