Mutational analysis of the N-capping box of the alpha-helix of chymotrypsin inhibitor 2.


The N-terminus of the helix of the chymotrypsin inhibitor 2 from barley (CI2) has an N-capping box (Ser at the first position in the helix and Glu at position 4) as well as a frequently found Glu at position 3. The energetic importance of this motif has been studied by determining the free energy of unfolding of the wild-type and protein mutants derived from those residues using guanidinium chloride-induced denaturation and differential scanning microcalorimetry. Mutating N-cap residue Ser31 to either Ala or Gly destabilizes CI2 by 0.8-1 kcal mol-1. Truncation of the box in the mutants SA31EA33EA34 or SG31EA33EA34 destablizes the protein by 1.5-2 kcal mol-1. The N-capping box is an important motif in stabilizing proteins and delineating the beginning of alpha-helices in the pathway of protein folding. Study holds ProTherm entries: 9801, 9802, 9803, 9804, 9805, 9806, 9807, 9808, 9809, 9810, 9811, 9812, 9813, 9814, 9815, 9816, 9817, 9818, 9819, 9820, 9821, 9822, 9823, 9824 Extra Details: helix stability; N-cap; protein folding; protein stability

Submission Details


Submitter: Connie Wang

Submission Date: April 24, 2018, 8:38 p.m.

Version: 1

Publication Details
elMasry NF;Fersht AR,Protein Eng. (1994) Mutational analysis of the N-capping box of the alpha-helix of chymotrypsin inhibitor 2. PMID:7937708
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 UniProtKB Entries

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