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Figure 7.
FIG. 7. HLA-B27-specific sandwich coordination of the
secondary anchor pArg1. A, stereo figure showing the clamp stack
involving pArg1 of the s10R peptide (red) and Arg-62, Glu-163,
and Trp167 from the HC (green). The alternative conformation of
Glu-163 is indicated in light green. Hydrogen bonds between
Arg-62, Glu-163, pArg1, and Wat58 are indicated with dotted
lines, and  - -stacking and hydrophobic
interactions by are indicated by stripes. B, the same region in
the B^*2709·m9 complex (PDB entry 1jge [PDB]
). Because the N-terminal pArg1 is missing in m9, no stacking is
present. Consequently, Trp-167 folds onto pGly1, and the Arg-62
side chain adopts a conformation parallel to helix  1. C and
D, for comparison two murine MHC molecules are shown. Both
feature a pArg1 but do not adopt the Arg-62-pArg1-Trp-167
sandwich conformation found in B^*2709·s10R. C,
H-2Kb·VSV8, PDB entry 1bqh [PDB]
, molecule 2. D, H-2D^d·HIV-1 (human immunodeficiency
virus 1), PDB entry 1bii [PDB]
.
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