Journal of Biochemistry Advance Access originally published online on July 4, 2008
Journal of Biochemistry 2008 144(4):457-466; doi:10.1093/jb/mvn088
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© 2008 The Japanese Biochemical Society.
The Unfolding of
-Momorcharin Proceeds Through the Compact Folded Intermediate
Institute of Biophysics, Faculty of Agriculture, Kyushu University, Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan
*To whom correspondence should be addressed. Tel/Fax: +81-92-642-4425, E-mail: yamashita{at}brs.kyushu-u.ac.jp
Received April 9, 2008; Accepted July 1, 2008
| Abstract |
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The unfolding of
-momorcharin was systematically investigated using steady-state and time-resolved tryptophan fluorescence, circular dichroism and 8-anilino-1-naphthalenesulfonic acid (ANS) binding. These spectroscopic studies demonstrated that
-momorcharin unfolded through a compact folded intermediate state. The content of
-helix was increased, Trp192 approached closer to the side of active site and its rotational motion was restricted by being equilibrated with 2–3 M of guanidine hydrochloride. Furthermore, the binding of ANS with
-momorcharin was more suppressed to show that the hydrophobic parts would not be accessed to the protein surface but rather be sealed off in this specific conformation state. These results suggest that the structure of
-momorcharin holds the more compact conformation as an incipient state for unfolding, which is the sharp contrast to β-momorcharin that gives the characteristics of the generally known molten globule state.
Key Words:
-momorcharin, fluorescence energy transfer, molten globule, protein folding/unfolding, time-resolved fluorescence depolarization
Abbreviations: ANS, 8-anilino-1-naphthalenesulfonic acid; CD, circular dichroism; Gdn, guanidine hydrochloride; MG, molten globule; RIPs, ribosome-inactivating proteins; TCSPC, time-correlated single photon counting