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Figure 7.
Figure 7. The site of the disulfide bond of 70--92.
A, Superposition of chain C of 70--92 on chain C of wild-
type (red). There are two different conformations of
mutant observed, type I (yellow) and type II (green)
(Table 5). These differ in the conformation of the disulfide
bond. B, Superposition of chain C of 70--92, type I only
(yellow), on chain C of wild-type (red), some side-
chain N atoms are shown in blue. The salt-bridge between
Arg 69 and Asp 93 in wild-type is disrupted in the mutant.
In the mutant crystal structure the side-chain is solvated
and incompletely defined. In the mutant the side-chain of
Lys66 occupies the cavity left by Arg69, but no hydrogen
bonds are formed with Asp93.
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