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Figure 2.
Figure 2 Structure of the HP1  shadow
domain/CAF-1 complex. (A) The backbone of residues 110 -172 of
HP1 and
214 -232 of CAF-1 from the 25 lowest energy structures (out of
72 that converged from the 100 computed). The structure has good
covalent geometry and nonbonded contacts (Table 1). The peptide
backbone around residues Asp-214 -Glu-219 of CAF-1 is not well
defined in the structure because only the Phe-217 and Ile-218
side chains interact with the shadow domain. 15N relaxation
studies show that the peptide backbone in this region has
increased mobility within the complex when compared to residues
in the PXVXL motif (Figure 1A). (B) The structure closest to the
mean, rotated by 90° about the z-axis, compared to the
orientation shown in (A). This structure is compared with that
of the free shadow domain (PDB code: 1DZ1; Brasher et al, 2000)
and the chromo domain/histone H3 complex (PDB code: 1GUW;
Nielsen et al, 2002). In the structure of the free shadow
domain, the side chains of Trp-170, which stabilise the position
of the C-terminal tails, are shown. (C) Stereoview of the
structure closest to the mean showing side chains of residues
involved in the HP1 /CAF-1
peptide interface. (D, E) Close-up views of the interactions
made by (D) Val-224 (position 0) and (E) Pro-222 and Leu-226
(positions -2/+2), Phe-217/Ile-218 (-7/-6 positions) and
Ile-229/Leu-230 (+5/+6 positions). In (A -D), the HP1 monomers
are coloured blue and magenta and the CAF-1 peptide is coloured
green. (Note: Trp-170 is not shown on monomer A because it does
not interact with Leu-226 at the +2 position.) 
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