Effect of cavity-creating mutations in the hydrophobic core of chymotrypsin inhibitor 2.


Abstract

Hydrophobic residues in the core of a truncated form of chymotrypsin inhibitor 2 (CI2) have been mutated in order to measure their contribution to the stability of the protein. The free energy of unfolding of wild-type and mutants was measured by both guanidinium chloride-induced denaturation and differential scanning calorimetry. The two methods give results for the changes in free energy on mutation that agree to within 1% or 2%. The average change in the free energy of unfolding (+/- standard deviation) for an Ile-->Val mutation is 1.2 +/- 0.1 kcal mol-1, for a Val-->Ala mutation 3.4 +/- 1.5 kcal mol-1, and for either an Ile-->Ala or a Leu-->Ala mutation 3.6 +/- 0.6 kcal mol-1. This gives an average change in the free energy of unfolding for deleting one methylene group of 1.3 +/- 0.5 kcal mol-1. Two significant correlations were found between the change in the free energy of unfolding between wild-type and mutant, delta delta GU-F, and the environment of the mutated residue in the protein. The first is between delta delta GU-F and the difference in side-chain solvent-accessible area buried between wild-type and mutant (correlation coefficient = 0.81, 10 points). The second and slightly better correlation was found between delta delta GU-F and N, the number of methyl/methylene groups within a 6-A radius of the hydrophobic group deleted (correlation coefficient = 0.84, 10 points). The latter correlation is very similar to that found previously for barnase, suggesting that this relationship is general and applies to the hydrophobic cores of other globular proteins. The combined data for C12 and barnase clearly show a better correlation with N (correlation coefficient = 0.87, 30 points) than with the change in the solvent-accessible surface area (correlation coefficient = 0.82, 30 points). This indicates that the packing density around a particular residue is important in determining the contribution the residue makes to protein stability. In one case, Ile-->Val76, a mutation which deletes the C delta 1 methyl group of a buried side chain, a surprising result was obtained. This mutant was found to be more stable than wild-type by 0.2 +/- 0.1 kcal mol-1. We have solved and analyzed the crystal structure of this mutant and find that there are small movements of side chains in the core, the largest of which, 0.7 A, is a movement of the side chain that has been mutated.(ABSTRACT TRUNCATED AT 400 WORDS) Study holds ProTherm entries: 1836, 1837, 1838, 1839, 1840, 1841, 1842, 1843, 1844, 1845, 1846, 1847, 1848, 1849, 1850, 1851, 1852, 1853, 1854, 1855, 1856, 1857, 1858, 1859, 1860, 1861, 1862, 13914, 13915, 13916, 13917, 13918, 13919, 13920, 13921, 13922, 13923, 13924, 13925, 13926 Extra Details: dG and ddG were measured in the presence of [GdnHCl]50%

Submission Details

ID: ahqsnk5x3

Submitter: Connie Wang

Submission Date: April 24, 2018, 8:18 p.m.

Version: 1

Publication Details
Jackson SE;Moracci M;elMasry N;Johnson CM;Fersht AR,Biochemistry (1993) Effect of cavity-creating mutations in the hydrophobic core of chymotrypsin inhibitor 2. PMID:8218191
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
1CIR 1996-01-29 COMPLEX OF TWO FRAGMENTS OF CI2 [(1-40)(DOT)(41-64)]
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
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
5FFN 2016-05-18 1.8 Complex of subtilase SubTY from Bacillus sp. TY145 with chymotrypsin inhibitor CI2A
1CQ4 1998-11-25 1.8 CI2 MUTANT WITH TETRAGLUTAMINE (MGQQQQGM) REPLACING MET59
5FBZ 2016-05-18 1.9 Structure of subtilase SubHal from Bacillus halmapalus - complex with chymotrypsin inhibitor CI2A
2CI2 1988-09-07 2.0 CRYSTAL AND MOLECULAR STRUCTURE OF THE SERINE PROTEINASE INHIBITOR CI-2 FROM BARLEY SEEDS
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
2SNI 1988-09-07 2.1 STRUCTURAL COMPARISON OF TWO SERINE PROTEINASE-PROTEIN INHIBITOR COMPLEXES. EGLIN-C-SUBTILISIN CARLSBERG AND CI-2-SUBTILISIN NOVO
1CIQ 1996-03-08 2.2 COMPLEX OF TWO FRAGMENTS OF CI2, RESIDUES 1-40 AND 41-64
1COA 1994-01-31 2.2 THE EFFECT OF CAVITY CREATING MUTATIONS IN THE HYDROPHOBIC CORE OF CHYMOTRYPSIN INHIBITOR 2

Relevant UniProtKB Entries

Percent Identity Matching Chains Protein Accession Entry Name
93.7 Subtilisin-chymotrypsin inhibitor-2A P08626 ICI3_HORVU
100.0 Subtilisin-chymotrypsin inhibitor-2A P01053 ICI2_HORVU
90.5 Subtilisin-chymotrypsin inhibitor-2A P82977 ICIW_WHEAT