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Figure 1.
Fig. 1. The crystal structure of DQ0602-hypocretin. (A) The
solvent-accessible surface of the DQ0602 peptide binding groove
is colored by electrostatic potential (blue, positive charge;
red, negative charge) viewed onto the TCR recognition surface.
The residues of the peptide are shown as ball-and-stick in
atomic coloring (blue, nitrogen; red, oxygen; yellow, peptide
carbon). The major pockets within the groove are labeled in the
standard MHC class II nomenclature. (B) A composite omit map
contoured at 1  is shown in blue
chicken wire. The peptide is depicted in ball-and-stick colored
as in A and viewed through the  1-helix. (C) A
superposition of the peptides from the DQ0602-hypocretin and
DQ0302-insulinB structures. The peptides are shown with atomic
coloring as in A except for the insulinB peptide carbon atoms
(green). The view is as in B, and the residues are labeled in
the standard MHC class II nomenclature. (D) Superposition of the
DQ0602 and DQ0302 peptide binding grooves. The C  traces
for DQ0602 (gray) and for DQ0302 (green) are viewed as in A. The
well ordered residues of the hypocretin peptide and linker are
shown with atomic coloring (peptide coloring as in A; orange,
linker carbon). Residues 46 to 55 and 85
to
91 show significant main
chain and side chain conformational changes between the two MHC
class II structures. The C positions of these
residues in DQ0602 are indicated by spheres (blue, -chain;
magenta, -chain). The concerted
conformational changes impact on the P1 pocket (see text) and on
the heterodimer interface. In particular, residue 48 changes
from leucine in DQ0302 to tryptophan in DQ0602, and the side
chain of Trp-48 (shown in blue sticks)
is reoriented to form a tight, hydrophobic interaction at the
interface with the 2 domain.
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