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Figure 5.
Figure 5. Structure of the β-barrel Cap in PduU
(A and
B) Cutaway views showing the side chain packing within the two
hexamer β-barrels. The side chains (sticks) of Met[10],
Gln[12], and Tyr[14] are buried within the β-barrel. Owing to
steric restrictions, all Gln[12] side chains were modeled in two
alternating conformations: “up” toward the N terminus and
“down” toward the C terminus. Interchain hydrogen bonding
between upward-oriented Gln[12] side chains is present in the
configuration shown in (A) (dashed line).
(C) Stereo view
of the PduU β-barrel viewed from its C-terminal end. Gln[12]
and other interior side chains are illustrated. The
configurations shown in both panels are from the hexamer labeled
“1” in the crystal asymmetric unit.
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