Folding of chymotrypsin inhibitor 2. 1. Evidence for a two-state transition.


Abstract

The reversible folding and unfolding of barley chymotrypsin inhibitor 2 (CI2) appears to be a rare example in which both equilibria and kinetics are described by a two-state model. Equilibrium denaturation by guanidinium chloride and heat is completely reversible, and the data can be fitted to a simple two-state model involving only native and denatured forms. The free energy of folding in the absence of denaturant, delta GH2O, at pH 6.3, is calculated to be 7.03 +/- 0.16 and 7.18 +/- 0.43 kcal mol-1 for guanidinium chloride and thermal denaturation, respectively. Scanning microcalorimetry shows that the ratio of the van't Hoff enthalpy of denaturation to the calorimetric enthalpy of denaturation does not deviate from unity, the value observed for a two-state transition, over the pH range 2.2-3.5. The heat capacity change for denaturation is found to be 0.789 kcal mol-1 K-1. The rate of unfolding of CI2 is first order and increases exponentially with increasing guanidinium chloride concentration. Refolding, however, is complex and involves at least three well-resolved phases. The three phases result from heterogeneity of the unfolded form due to proline isomerization. The fast phase, 77% of the amplitude, corresponds to the refolding of the fraction of the protein that has all its prolines in a native trans conformation. The rate of this major phase decreases exponentially with increasing guanidinium chloride concentration. The unfolding and refolding kinetics can also be fitted to a two-state model.(ABSTRACT TRUNCATED AT 250 WORDS) Study holds ProTherm entries: 2953, 2954, 2955, 2956, 2957, 11831, 11832, 11833, 11834, 11835 Extra Details: dG was calculated at 25 degrees C

Submission Details

ID: W82SgH2Q3

Submitter: Connie Wang

Submission Date: April 24, 2018, 8:20 p.m.

Version: 1

Publication Details
Jackson SE;Fersht AR,Biochemistry (1991) Folding of chymotrypsin inhibitor 2. 1. Evidence for a two-state transition. PMID:1931967
Additional Information

Structure view and single mutant data analysis

Study data

No weblogo for data of varying length.
Colors: D E R H K S T N Q A V I L M F Y W C G P
 

Data Distribution

Studies with similar sequences (approximate matches)

Correlation with other assays (exact sequence matches)


Relevant PDB Entries

Structure ID Release Date Resolution Structure Title
3CI2 1993-10-31 REFINEMENT OF THE THREE-DIMENSIONAL SOLUTION STRUCTURE OF BARLEY SERINE PROTEINASE INHIBITOR 2 AND COMPARISON WITH THE STRUCTURES IN CRYSTALS
1CIS 1993-10-31 CONTEXT DEPENDENCE OF PROTEIN SECONDARY STRUCTURE FORMATION. THE THREE-DIMENSIONAL STRUCTURE AND STABILITY OF A HYBRID BETWEEN CHYMOTRYPSIN INHIBITOR 2 AND HELIX E FROM SUBTILISIN CARLSBERG
1CIR 1996-01-29 COMPLEX OF TWO FRAGMENTS OF CI2 [(1-40)(DOT)(41-64)]
1LW6 2002-08-21 1.5 Crystal Structure of the Complex of Subtilisin BPN' with Chymotrypsin Inhibitor 2 at 1.5 Angstrom Resolution
1YPC 1994-01-31 1.7 DIRECT OBSERVATION OF BETTER HYDRATION AT THE N-TERMINUS OF AN ALPHA-HELIX WITH GLYCINE RATHER THAN ALANINE AS N-CAP
1CQ4 1998-11-25 1.8 CI2 MUTANT WITH TETRAGLUTAMINE (MGQQQQGM) REPLACING MET59
5FFN 2016-05-18 1.8 Complex of subtilase SubTY from Bacillus sp. TY145 with chymotrypsin inhibitor CI2A
5FBZ 2016-05-18 1.9 Structure of subtilase SubHal from Bacillus halmapalus - complex with chymotrypsin inhibitor CI2A
1YPA 1994-01-31 2.0 DIRECT OBSERVATION OF BETTER HYDRATION AT THE N-TERMINUS OF AN ALPHA-HELIX WITH GLYCINE RATHER THAN ALANINE AS N-CAP
1YPB 1994-01-31 2.0 DIRECT OBSERVATION OF BETTER HYDRATION AT THE N-TERMINUS OF AN ALPHA-HELIX WITH GLYCINE RATHER THAN ALANINE AS N-CAP
2CI2 1988-09-07 2.0 CRYSTAL AND MOLECULAR STRUCTURE OF THE SERINE PROTEINASE INHIBITOR CI-2 FROM BARLEY SEEDS
2SNI 1988-09-07 2.1 STRUCTURAL COMPARISON OF TWO SERINE PROTEINASE-PROTEIN INHIBITOR COMPLEXES. EGLIN-C-SUBTILISIN CARLSBERG AND CI-2-SUBTILISIN NOVO
1COA 1994-01-31 2.2 THE EFFECT OF CAVITY CREATING MUTATIONS IN THE HYDROPHOBIC CORE OF CHYMOTRYPSIN INHIBITOR 2
1CIQ 1996-03-08 2.2 COMPLEX OF TWO FRAGMENTS OF CI2, RESIDUES 1-40 AND 41-64

Relevant UniProtKB Entries

Percent Identity Matching Chains Protein Accession Entry Name
95.6 Chymotrypsin inhibitor 2 P08626 ICI3_HORVU
100.0 Subtilisin-chymotrypsin inhibitor-2A P01053 ICI2_HORVU