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Figure 3.
Figure 3. Crystal Structure of the Homer Coiled-Coil Region
(A) Ribbon representation of the crystal structure of the
C-terminal half of Homer1b coiled-coil region CC2. The four
strands are marked A–D.
(B) A model of the whole
structure of long form of Homer. The model is constructed from
the structure of the Homer1CC2 domain (blue), EVH1 domain (red)
(Irie et al., 2002), and coiled-coil probability prediction and
protease degradation sites (Hayashi et al., 2006). The CC1 and a
part of the CC2 domain, whose atomic structures are not known,
are in light green and light blue, respectively. Regions likely
to be disordered are shown in gray.
(C) Primary sequence of
the crystallized fragment. 1B, rat Homer1b; 3A, human Homer3a.
Orange, aliphatic residues (I, L, V); blue, acidic (D, E);
green, basic (K, R); gray, residues not in crystals. Mutations
made in dimeric Homer1b I332R/I337E are shown below.
“abcdefg” denotes positions in the heptad of coiled coil.
(D) Distance between the A and the B strand or between the
C and the D strand are measured and plotted against the number
of residues.
(E) Helical wheel representation of the
dimeric (top) and tetrameric (bottom) region of Homer1b.
Residues start from K290 at g position. Residues that make
knobs-into-holes interactions with residues on the other strands
are shown in blue. Residues changed in the dimeric mutant (I332
and I337) are shown in red. Residues outside the dotted circles
are located within the wide dimeric region.
(F) Example of
intermolecular salt bridges formed between residues at the e
(E295 and E302) and g (K290 and R297) positions within the
dimeric region.
(G) Large amino acids occupying the a and d
positions in the wide dimeric region, Q319 and F322.
(H)
Interchain interactions in the tetrameric region. Residues at d
positions (L329, K336, L343, L350) form the A-D and B-C
interface, and those at e positions (L330, I337, R344, L351)
form the A-C and B-D interface.
(I) Hydrophobic core formed
by leucines at a positions (L326, L333, L340, L347).
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