|
Figure 3.
FIGURE 3. Structural analysis of the p62 UBA domain and the
binding surfaces of the UBA and mUb. Chemical shift
perturbations are mapped to the surface of Ub on a linear scale
of white to red (largest) (A), as described by the data in Fig.
2B. B, surface representation of the structure of the p62-UBA
domain in the Ub-bound state showing the surface charge
distribution (acidic, red, and basic, blue) and hydrophobicity
(white). The structure is viewed toward the Met-Gly-Phe-Ser loop
region. C, identical orientation and representation of the UBA
domain of p62 showing secondary fast exchange chemical shift
perturbations (red) indicative of binding interactions with mUb.
These binding perturbations correlate well with the hydrophobic
surface shown in B, comprising residues within loop 1 and the C
terminus of helix 3. Ribbon diagram shows NMR structures of the
unbound UBA domain (D) and the bound form in the presence of 6
eq of mUb (E). The structural statistics are shown in Table 1.
In the unbound state the environment of the side chain of
Gln^400 is defined by NOEs with residues Phe^406, Ile^424, and
Leu^428 (F); in contrast, the repacking of the helices in the
bound state shows that Gln^400 is close in space to Trp^412,
Leu^416, and Leu^417 (G). In this conformation the side chains
of Phe^406, Ile^424, and Leu^428 are more remote from Gln^400. A
schematic representation of the two structures is shown to
illustrate more clearly the structural reorganization and
repacking of the three helices that occurs (H). The cylindrical
arrows represent the orientation and polarity of the helices. H,
free (blue) and bound (red) structures are shown with a common
alignment of helices 1 and 2. These structures are superimposed
in I, showing the different positions and orientations of helix
3 in the two forms.
|
