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Figure 6.
Figure 6. The structure of G4-G6 at pH 4.5. (a) A stereo
cartoon representation of the high-resolution structure of G4-G6
subjected to the initial wash conditions at pH 4.5. The domains
are coloured: G4, pink; G5, green; and G6, orange. The terbium
anomalous electron density map, contoured at 5 s (cyan), is
superimposed onto the structure. Three terbium ion positions,
characterized by the positive density in this map, are identical
with the positions of type II calcium ions in this
high-resolution structure and are labeled G4:II, G5:II and
G6:II. The fourth terbium ion (G4:I) is in a position where
calcium is not found in the high-resolution structure, but is
found in the G4-G6:actin structure.15 (b) A cartoon
representation of G4-G6 taken from the calcium-free form of
gelsolin (PDB i.d. 1D0N),6 for purposes of comparison. In this
state, the core b-sheet of G4 (pink) abuts that of G6 (orange),
constituting the G4-G6 latch.15
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