Thermodynamic study of the acid denaturation of barnase and its dependence on ionic strength: evidence for residual electrostatic interactions in the acid/thermally denatured state.


Abstract

We have investigated the acid denaturation of barnase and its dependence on ionic strength. From the pH dependence of the protein stability, we have obtained information about the titration properties of the native and denatured protein at temperatures ranging from 15 to 60 degrees C in the absence of chemical denaturant. It appears that both the native and the denatured state of barnase titrates at higher pH values in the presence of salt. The observation suggests that charge interactions are present, not only within the native fold but also within the denatured state, and that these interactions contribute to shift the pKa values from those of isolated model compounds. Upon addition of salt these repulsive interactions are shielded, and the electrostatic free energy of the native state, as well as the denatured state, is reduced. Accordingly, we suggest that the thermally denatured state of barnase is not an extended random coil without residue-residue interactions but is sufficiently compact to contain intramolecular charge-charge repulsions. The results further reveal that the native state of barnase contains at least one residue with a highly anomalous pKa value: At pH 0.3, the difference in degree of protonation between the native and the denatured state is still about 1 mol H+/mol protein. Study holds ProTherm entries: 4498 Extra Details: electrostatic interactions; random coil; protonation;,residue-residue interactions; charge-charge repulsions

Submission Details

ID: rH3frYkY3

Submitter: Connie Wang

Submission Date: April 24, 2018, 8:25 p.m.

Version: 1

Publication Details
Oliveberg M;Vuilleumier S;Fersht AR,Biochemistry (1994) Thermodynamic study of the acid denaturation of barnase and its dependence on ionic strength: evidence for residual electrostatic interactions in the acid/thermally denatured state. PMID:8038174
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
1A2P 1998-01-07T00:00:00+0000 1.5 BARNASE WILDTYPE STRUCTURE AT 1.5 ANGSTROMS RESOLUTION
1B20 1998-12-03T00:00:00+0000 1.7 DELETION OF A BURIED SALT-BRIDGE IN BARNASE
1B21 1998-12-03T00:00:00+0000 2.0 DELETION OF A BURIED SALT BRIDGE IN BARNASE
1B27 1998-12-04T00:00:00+0000 2.1 STRUCTURAL RESPONSE TO MUTATION AT A PROTEIN-PROTEIN INTERFACE
1B2S 1998-11-30T00:00:00+0000 1.82 STRUCTURAL RESPONSE TO MUTATION AT A PROTEIN-PROTEIN INTERFACE
1B2U 1998-12-01T00:00:00+0000 2.1 STRUCTURAL RESPONSE TO MUTATION AT A PROTEIN-PROTEIN INTERFACE
1B2X 1998-12-03T00:00:00+0000 1.8 BARNASE WILDTYPE STRUCTURE AT PH 7.5 FROM A CRYO_COOLED CRYSTAL AT 100K
1B2Z 1998-12-03T00:00:00+0000 2.03 DELETION OF A BURIED SALT BRIDGE IN BARNASE
1B3S 1998-12-01T00:00:00+0000 2.39 STRUCTURAL RESPONSE TO MUTATION AT A PROTEIN-PROTEIN INTERFACE
1BAN 1993-05-19T00:00:00+0000 2.2 THE CONTRIBUTION OF BURIED HYDROGEN BONDS TO PROTEIN STABILITY: THE CRYSTAL STRUCTURES OF TWO BARNASE MUTANTS

Relevant UniProtKB Entries

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