Comparison of the hydrogen-exchange behavior of reduced and oxidized Escherichia coli thioredoxin

Modern NMR techniques enable the determination of the amide proton exchange rates in oxidized and reduced Escherichia coli thioredoxin. Backbone mobility of the amide proton is estimated from these exchange rates. Oxidized thioredoxin exhibits lower exchange rate for Cys 35 amide proton compared to reduced thioredoxin. The higher exchange rate for reduced forms reveals that reduction loosens the structure of the protein. Greater flexibility of the reduced form accounts for the functional differences between two forms.