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
Submitter: Connie Wang
Submission Date: April 24, 2018, 8:38 p.m.
|Number of data points||55|
|Proteins||Subtilisin-chymotrypsin inhibitor-2A ; Subtilisin-chymotrypsin inhibitor-2A|
|Assays/Quantities/Protocols||Experimental Assay: ddG pH:3.0, buffers:glycine-HCl: 10 mM ; Experimental Assay: ddG buffers:formate: 10 mM, pH:3.5 ; Experimental Assay: dHcal pH:3.0, buffers:glycine-HCl: 10 mM ; Experimental Assay: Tm pH:3.0, buffers:glycine-HCl: 10 mM ; Experimental Assay: dHcal buffers:formate: 10 mM, pH:3.5 ; Experimental Assay: Tm buffers:formate: 10 mM, pH:3.5 ; Experimental Assay: Cm ; Experimental Assay: m ; Experimental Assay: dG_H2O|
|Libraries||Mutations for sequence SSVEKKPEGVNTGAGDRHNLKTEWPELVGKSVEEAKKVILQDKPEAQIIVLPVGTIVTMEYRIDRVRLFVDKLDNIAEVPRVG|