Co-operative interactions during protein folding.


Abstract

The theory for measuring co-operativity between interactions in proteins by protein engineering experiments is developed by introducing a procedure for analysing increasing orders of synergy in a protein with increasing numbers of residues. The (pairwise) interaction energy (delta 2Gint) between two side-chains may be measured experimentally by a double-mutant cycle consisting of the wild-type protein, the two single mutants and the double mutant. This procedure may be extended to three residues to give a value for delta 3Gint for a triple-mutant cube, and to higher orders using multi-dimensional mutant space. We now show that delta 3Gint is the excess energy of adding all three chains compared with the sum of all the pairwise values of delta 2Gint for each of the constituent double-mutant cycles and the sum of all the single addition energies. This physical interpretation extends to higher orders of mutation. delta nGint (i.e. the interaction energy for n residues), thus, reveals the layers of synergy in interactions as a protein is built up. This procedure is applied to measuring changes in synergy during the refolding of barnase for the triad of salt-linked residues Asp8, Asp12 and Arg110, which are mutated to alanine residues. The value of delta 3Gint in the folded structure is 0.77(+/- 0.06) kcal mol-1 (i.e. the triad is 0.77 kcal mol-1 more stable than expected from the sum of the individual pairwise interactions and single contributions). The value of delta 3Gint is still significant in the transition state for unfolding (0.60(+/- 0.07) kcal mol-1) and in the folding intermediate (0.60(+/- 0.13 kcal mol-1)). These results show that synergistic interactions exist in barnase, in its transition state for unfolding and in a refolding intermediate. A direct measurement of the change of co-operativity between the folded state and the transition state for unfolding shows a decrease of 0.17(+/- 0.04) kcal mol-1, suggesting that the initial stages of protein unfolding may be accompanied by some loosening of structure in parts that still interact. The similar extent of co-operativity in the transition state for unfolding and the intermediate in refolding suggests that the intermediate is homogeneous, at least in the region of the salt-linked triad, as heterogeneity would lower the co-operativity. Study holds ProTherm entries: 7470, 7471, 7472, 7473, 7474, 7475, 7476, 7477 Extra Details: barnase; protein stability; protein folding;,protein engineering; mutagenesis

Submission Details

ID: vWgfrMbu

Submitter: Connie Wang

Submission Date: April 24, 2018, 8:34 p.m.

Version: 1

Publication Details
Horovitz A;Fersht AR,J. Mol. Biol. (1992) Co-operative interactions during protein folding. PMID:1569552
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
2KF5 2009-12-08 Barnase bound to d(CGAC), low pressure
2KF4 2009-12-08 Barnase high pressure structure
2KF3 2009-12-08 Barnase, low pressure reference NMR structure
1BNR 1995-07-31 BARNASE
1FW7 2003-06-10 NMR STRUCTURE OF 15N-LABELED BARNASE
2KF6 2009-12-08 Barnase bound to d(CGAC) high pressure
2C4B 2005-11-21 1.3 Inhibitor cystine knot protein McoEeTI fused to the catalytically inactive barnase mutant H102A
1A2P 1998-04-29 1.5 BARNASE WILDTYPE STRUCTURE AT 1.5 ANGSTROMS RESOLUTION
2ZA4 2008-05-20 1.58 Crystal Structural Analysis of Barnase-barstar Complex
1B20 1998-12-09 1.7 DELETION OF A BURIED SALT-BRIDGE IN BARNASE
1BRN 1994-01-31 1.76 SUBSITE BINDING IN AN RNASE: STRUCTURE OF A BARNASE-TETRANUCLEOTIDE COMPLEX AT 1.76 ANGSTROMS RESOLUTION
1B2X 1998-12-09 1.8 BARNASE WILDTYPE STRUCTURE AT PH 7.5 FROM A CRYO_COOLED CRYSTAL AT 100K
1B2S 1998-12-08 1.82 STRUCTURAL RESPONSE TO MUTATION AT A PROTEIN-PROTEIN INTERFACE
1RNB 1992-07-15 1.9 CRYSTAL STRUCTURE OF A BARNASE-D(*GP*C) COMPLEX AT 1.9 ANGSTROMS RESOLUTION
1X1Y 2005-04-26 1.9 Water-mediate interaction at aprotein-protein interface
1BRI 1995-07-10 1.9 BARNASE MUTANT WITH ILE 76 REPLACED BY ALA
3KCH 2010-03-09 1.94 Baranase crosslinked by glutaraldehyde
2F5M 2006-04-25 1.95 Cross-linked barnase soaked in bromo-ethanol
2F56 2006-04-25 1.96 Barnase cross-linked with glutaraldehyde soaked in 6M urea
1BRS 1994-06-22 2.0 PROTEIN-PROTEIN RECOGNITION: CRYSTAL STRUCTURAL ANALYSIS OF A BARNASE-BARSTAR COMPLEX AT 2.0-A RESOLUTION
1BRH 1995-07-10 2.0 BARNASE MUTANT WITH LEU 14 REPLACED BY ALA
2F5W 2006-04-25 2.0 Cross-linked barnase soaked in 3 M thiourea
1BSE 1994-01-31 2.0 CRYSTAL STRUCTURAL ANALYSIS OF MUTATIONS IN THE HYDROPHOBIC CORES OF BARNASE
1BSC 1994-01-31 2.0 CRYSTAL STRUCTURAL ANALYSIS OF MUTATIONS IN THE HYDROPHOBIC CORES OF BARNASE
1BNF 1995-07-10 2.0 BARNASE T70C/S92C DISULFIDE MUTANT
1BSB 1994-01-31 2.0 CRYSTAL STRUCTURAL ANALYSIS OF MUTATIONS IN THE HYDROPHOBIC CORES OF BARNASE
1BSA 1994-01-31 2.0 CRYSTAL STRUCTURAL ANALYSIS OF MUTATIONS IN THE HYDROPHOBIC CORES OF BARNASE
1B21 1998-12-09 2.0 DELETION OF A BURIED SALT BRIDGE IN BARNASE
1BRJ 1995-07-10 2.0 BARNASE MUTANT WITH ILE 88 REPLACED BY ALA
1BRK 1995-07-10 2.0 BARNASE MUTANT WITH ILE 96 REPLACED BY ALA
1B2Z 1998-12-09 2.03 DELETION OF A BURIED SALT BRIDGE IN BARNASE
1BNS 1994-06-22 2.05 STRUCTURAL STUDIES OF BARNASE MUTANTS
1BNG 1995-07-10 2.1 BARNASE S85C/H102C DISULFIDE MUTANT
1BNI 1995-09-15 2.1 BARNASE WILDTYPE STRUCTURE AT PH 6.0
1B27 1998-12-09 2.1 STRUCTURAL RESPONSE TO MUTATION AT A PROTEIN-PROTEIN INTERFACE
1X1W 2005-04-26 2.1 Water-mediate interaction at aprotein-protein interface
1BNJ 1995-09-15 2.1 BARNASE WILDTYPE STRUCTURE AT PH 9.0
1B2U 1998-12-09 2.1 STRUCTURAL RESPONSE TO MUTATION AT A PROTEIN-PROTEIN INTERFACE
1BNE 1995-07-10 2.1 BARNASE A43C/S80C DISULFIDE MUTANT
2F4Y 2006-04-25 2.15 Barnase cross-linked with glutaraldehyde
3Q3F 2012-01-25 2.17 Engineering Domain-Swapped Binding Interfaces by Mutually Exclusive Folding: Insertion of Ubiquitin into position 103 of Barnase
1BAN 1993-10-31 2.2 THE CONTRIBUTION OF BURIED HYDROGEN BONDS TO PROTEIN STABILITY: THE CRYSTAL STRUCTURES OF TWO BARNASE MUTANTS
1BRG 1994-06-22 2.2 CRYSTALLOGRAPHIC ANALYSIS OF PHE->LEU SUBSTITUTION IN THE HYDROPHOBIC CORE OF BARNASE
1BAO 1993-10-31 2.2 THE CONTRIBUTION OF BURIED HYDROGEN BONDS TO PROTEIN STABILITY: THE CRYSTAL STRUCTURES OF TWO BARNASE MUTANTS
1YVS 1999-02-02 2.2 Trimeric domain swapped barnase
3DA7 2009-04-14 2.25 A conformationally strained, circular permutant of barnase
1X1U 2005-04-26 2.3 Water-mediate interaction at aprotein-protein interface
1BSD 1994-01-31 2.3 CRYSTAL STRUCTURAL ANALYSIS OF MUTATIONS IN THE HYDROPHOBIC CORES OF BARNASE
1X1X 2005-04-26 2.3 Water-mediate interaction at aprotein-protein interface
1B3S 1998-12-09 2.39 STRUCTURAL RESPONSE TO MUTATION AT A PROTEIN-PROTEIN INTERFACE
1BGS 1994-04-30 2.6 RECOGNITION BETWEEN A BACTERIAL RIBONUCLEASE, BARNASE, AND ITS NATURAL INHIBITOR, BARSTAR

Relevant UniProtKB Entries

Percent Identity Matching Chains Protein Accession Entry Name
97.3 Ribonuclease P35078 RN_BACCI
100.0 Ribonuclease P00648 RNBR_BACAM