Conversion of two-state to multi-state folding kinetics on fusion of two protein foldons

Kenji Inaba, Naohiro Kobayashi, Alan R. Fersht

Research output: Contribution to journalArticlepeer-review

25 Citations (Scopus)


Chymotrypsin inhibitor 2 (CI2) is the archetypal single-foldon protein that folds in simple two-state kinetics without the accumulation of a folding intermediate. To model the effects of fusion of single foldons to give a multi-foldon protein, we engineered a 'double-CI2' protein, in which another CI2 polypeptide was inserted into the loop region of the parent CI2. CD and HSQC spectra demonstrated that while the double-CI2 protein adopted two kinds of native conformations, CI2-like structure was almost preserved in both the domains of double-CI2. In the folding kinetic studies, double-CI2 exhibited a remarkable rollover of the observed folding rates at low denaturant concentrations, indicating that double-CI2 accumulated a kinetic folding intermediate. The different folding mechanisms between WT-CI2 and double-CI2 support the present view that protein size or number of domains is an important determinant for formation of folding intermediates. (C) 2000 Academic Press.

Original languageEnglish
Pages (from-to)219-233
Number of pages15
JournalJournal of Molecular Biology
Issue number1
Publication statusPublished - 2000 Sept 8


  • CI2
  • Folding intermediate
  • Foldon
  • Protein design


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