Denaturant-Induced Conformational Transitions in Intrinsically Disordered Proteins

Intrinsically disordered proteins (IDPs) differ from ordered proteins at several levels: structural, functional, and conformational. Amino acid biases also drive atypical responses of IDPs to changes in their environ- ment. Among several specific features, the conformational behavior of IDPs is characterized by the low cooperativity (or the complete lack thereof) of the denaturant-induced unfolding. In fact, the denaturant- induced unfolding of native molten globules can be described by shallow sigmoidal curves, whereas urea- or guanidinium hydrochloride-induced unfolding of native pre-molten globules or native coils is a noncoop- erative process and typically is seen as monotonous feature-less changes in the studied parameters. This chapter describes some of the most characteristic features of the IDP conformational behavior.