FIGURE 1.

Oxidative folding and reductive unfolding of LDTI. RP-HPLC traces of the folding (A) and unfolding (B) intermediates trapped by acidification over time. The folding reactions were performed in the absence (Control −) or presence (Control +) of 0.25 mm 2-mercaptoethanol as thiol catalyst, the unfolding reactions using 1 mm TCEP as reducing agent. Retention times of the native (N) and fully reduced/unfolded (R) forms as well as the major intermediates are labeled. I represents a major intermediate with one native disulfide bond. I* represents a group of native and non-native 1-disulfide intermediates. IIa, IIb, and IIc constitute the major intermediates comprising two native disulfide bonds.