Visualization of the nanospring dynamics of the IkappaBalpha ankyrin repeat domain in real time.

ABSTRACT: I?B? is a crucial regulator of NF?B transcription. NF?B-mediated gene activation is robust because levels of free I?B? are kept extremely low by rapid, ubiquitin-independent degradation of newly synthesized I?B?. I?B? has a weakly folded ankyrin repeat 5-6 (AR5-6) region that is critical in establishing its short intracellular half-life. The AR5-6 region of I?B? folds upon binding to NF?B. The NF?B-bound I?B? has a long half-life and requires ubiquitin-targeted degradation. We present single molecule FRET evidence that the native state of I?B? transiently populates an intrinsically disordered state characterized by a more extended structure and fluctuations on the millisecond time scale. Binding to NF?B or introduction of stabilizing mutations in AR 6 suppressed the fluctuations, whereas higher temperature or small amounts of urea increased them. The results reveal that intrinsically disordered protein regions transition between collapsed and extended conformations under native conditions.

SUBMITTER: Lamboy JA 

PROVIDER: S-EPMC3121830 | biostudies-literature | 2011 Jun

REPOSITORIES: biostudies-literature