Figure 2.
Figure 2. The homophilic binding interface of NCAM. a, Space
filling model of the interaction interface of the NCAM IgI-IgII
dimer. To illustrate the complementarity of the residues in the
two molecules, molecule A (blue) in the A -B dimer has been
rotated 180° around the vertical axis, away from molecule B
(pink), compared to Fig. 1b. Residues involved in homophilic
binding are clustered near the IgI-IgII linker region, and these
residues are color coded. Two salt bridges (Glu A16 -Lys B98 and
vice versa) in the linker region (red) are surrounded by two
patches of important residues, one in each of the IgI and IgII
domains. Residues that participate in polar interactions (Ser
17, Thr 61, Thr 63, Arg 169, Glu 171, Arg 177, and Asn 181 in
both molecules) are dark blue. Residues mainly involved in
hydrophobic interactions (Val 6, cis Pro 7, Lys 18, Leu 175, Ala
176, Glu 179 and Phe 182 in both molecules) are green. The
residues in yellow (Phe 19, Tyr 65, Arg 173, Gly 178 and Ile 180
in both molecules) participate in hydrophobic as well as polar
interactions. b, Close up view of the interaction interface in
the A -B dimer described in (a). Ribbon representations of -strands
from molecule A and B are shown in transparent blue and pink,
respectively. Residues involved in homophilic binding are
represented as ball-and-stick models with carbon atoms from
molecule A colored green, and residues from molecule B colored
purple. A water molecule is shown as a red sphere. Red atoms
indicate oxygen, and blue atoms nitrogen. At the dimer interface
two conserved aromatic residues, Phe 19 and Tyr 65 from two
opposite antiparallel strands in molecule A, intercalate into
pockets created by a hairpin motif in molecule B. Phe 19 is
shielded by hydrophobic interactions, whereas Tyr 65
participates in hydrophobic as well as polar interactions.
Hydrogen bonds are shown as red dashed lines. c, Stereo view of
the final 2F[o] - F[c] electron density map contoured at 1 level,
showing the intercalation of Phe A19 into a pocket in molecule B
made up of residues B173 -B178.
The above figure is reprinted
by permission from Macmillan Publishers Ltd:
Nat Struct Biol
(2000,
7,
389-393)
copyright 2000.
-strands
from molecule A and B are shown in transparent blue and pink,
respectively. Residues involved in homophilic binding are
represented as ball-and-stick models with carbon atoms from
molecule A colored green, and residues from molecule B colored
purple. A water molecule is shown as a red sphere. Red atoms
indicate oxygen, and blue atoms nitrogen. At the dimer interface
two conserved aromatic residues, Phe 19 and Tyr 65 from two
opposite antiparallel strands in molecule A, intercalate into
pockets created by a hairpin motif in molecule B. Phe 19 is
shielded by hydrophobic interactions, whereas Tyr 65
participates in hydrophobic as well as polar interactions.
Hydrogen bonds are shown as red dashed lines. c, Stereo view of
the final 2F[o] - F[c] electron density map contoured at 1 
level,
showing the intercalation of Phe A19 into a pocket in molecule B
made up of residues B173 -B178.