Molecular model showing destabilization of the linker (blue) between repeats 4 and 5 as a result of the Q471P substitution. The mutated site and nearby Cys⁴⁷⁵ are shown in green and yellow, respectively. Disruption in the helix in the linker increases exposure of the Cys⁴⁷⁵. See the complete figure in the article beginning on page 3538.