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Figure 3.
Fig. 3. Stereoviews of the structure and hydrogen bonding of
the extracellular region in the BR state (A) and the M state
(B). The extensive hydrogen-bonding network leading to the
extracellular surface found in the BR state is fragmented in the
M state. Notable are new hydrogen bonds formed in the M state
between Trp86 NE and Asp212 OD-1 and between Tyr83 OH and Glu194
OE-1; the carboxylate side chain of Asp85 has lost a hydrogen
bond from Thr89 OH; the guanidinium moiety of Arg82 has moved
away from the Schiff base and toward the extracellular side
(downward) by 1.7 Å, largely because of a rotation around
 [3] by
60°.
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