Download MendeleyDetection and structure determination of an equilibrium unfolding intermediates of Rd-apocytochrome b562: native fold with non-native hydrophobic interactions
Feng, H., Vu, N., Bai, Y.(2004) J Mol Biology 343: 1477-1485
- PubMed: 15491625 Search on PubMed
- DOI: https://doi.org/10.1016/j.jmb.2004.08.099
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1YYX - PubMed Abstract:
The absence of detectable kinetic and equilibrium folding intermediates by optical probes is commonly taken to indicate that protein folding is a two-state process. However, for some small proteins with apparent two-state behavior, unfolding intermediates have been identified in native-state hydrogen exchange or kinetic unfolding experiments monitored by nuclear magnetic resonance. Rd-apocytochrome b(562), a four-helix bundle, is one such protein. Here, we found another unfolding intermediate for Rd-apocytochrome b(562). It is based on a cooperative transition of (15)N chemical shifts of amide protons as a function of urea concentrations before the global unfolding. We have solved the high-resolution structure of the protein at 2.8 M urea, which is after this cooperative transition but before the global unfolding. All four helices remained intact, but a number of hydrophobic core residues repacked. This intermediate provides a possible structural interpretation for the kinetic unfolding intermediates observed using nuclear magnetic resonance methods for several proteins and has important implications for theoretical studies of protein folding.
- Laboratory of Biochemistry, National Cancer Institute, NIH, Building 37, Room 6114E, Bethesda, MD 20892, USA.
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