Fig. 3: The intermediate I refolds to the native state N at low membrane potentials.
From: Free-energy landscapes of membrane co-translocational protein unfolding
a The intermediate produced at +120 mV was monitored after a step to +45 mV (asterisk). This state (I*) could either complete unfolding and translocate (left trace) or convert to a low-conductance level that resembled the native state (N*, right trace). At +45 mV, 55% of the molecules (n = 92) transitioned to the low-conductance level. The analysis of 524 molecules over the range +30 to +60 mV revealed a sigmoidal dependence of the probability to transition to N* on the applied potential. b The newly produced native state (N*) was re-exposed to +120 mV (double asterisk) and the co-translocational unfolding of N** was recorded. c The lifetimes of the N and N** states showed similar distributions and were fitted to exponentials, yielding kN→I = 24 ± 4 s−1 (n = 115) and kN**→I** = 37 ± 19 s−1 (n = 115), suggesting that both N and N** were natively folded proteins. d The lifetimes of the I and I** states show similar distributions and were fitted to exponentials yielding kI→T = 2.8 ± 0.5 s−1 (n = 198) and kI**→T = 2.3 ± 0.6 s−1 (n = 115), suggesting that I and I** have similar stabilities.
