Protein interactions with urea and guanidinium chloride. A calorimetric study.


The interaction of urea and guanidinium chloride with proteins has been studied calorimetrically by titrating protein solutions with denaturants at various fixed temperatures, and by scanning them with temperature at various fixed concentrations of denaturants. It has been shown that the observed heat effects can be described in terms of a simple binding model with independent and similar binding sites. Using the calorimetric data, the number of apparent binding sites for urea and guanidinium chloride have been estimated for three proteins in their unfolded and native states (ribonuclease A, hen egg white lysozyme and cytochrome c). The intrinsic and total thermodynamic characteristics of their binding (the binding constant, the Gibbs energy, enthalpy, entropy and heat capacity effect of binding) have also been determined. It is found that the binding of urea and guanidinium chloride by protein is accompanied by a significant decrease of enthalpy and entropy. At all concentrations of denaturants the enthalpy term slightly dominates the entropy term in the Gibbs energy function. Correlation analysis of the number of binding sites and structural characteristics of these proteins suggests that the binding sites for urea and guanidinium chloride are likely to be formed by several hydrogen bonding groups. This type of binding of the denaturant molecules should lead to a significant restriction of conformational freedom within the polypeptide chain. This raises a doubt as to whether a polypeptide chain in concentrated solutions of denaturants can be considered as a standard of a random coil conformation. Study holds ProTherm entries: 2995, 2996 Extra Details: proteins; denaturants; denaturation; thermodynamics; calorimetry

Submission Details

ID: 3dvUoqDj

Submitter: Connie Wang

Submission Date: April 24, 2018, 8:20 p.m.

Version: 1

Publication Details
Makhatadze GI;Privalov PL,J. Mol. Biol. (1992) Protein interactions with urea and guanidinium chloride. A calorimetric study. PMID:1322462
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 Ribonuclease pancreatic P61824 RNAS1_BISBI
100.0 Ribonuclease pancreatic P61823 RNAS1_BOVIN
96.8 Ribonuclease pancreatic P67926 RNAS1_CAPHI
96.8 Ribonuclease pancreatic P67927 RNAS1_SHEEP
95.2 Ribonuclease pancreatic P00657 RNAS1_BUBBU
96.0 Ribonuclease pancreatic P07847 RNAS1_AEPME
93.5 Ribonuclease pancreatic P07848 RNAS1_EUDTH
95.2 Ribonuclease pancreatic P00660 RNAS1_CONTA
92.7 Ribonuclease pancreatic P00668 RNAS1_ANTAM
90.3 Ribonuclease pancreatic P00662 RNAS1_GIRCA
96.0 Ribonuclease pancreatic Q29606 RNAS1_ORYLE
100.0 Lysozyme C P00698 LYSC_CHICK
96.9 Lysozyme C P00700 LYSC_COLVI
96.9 Lysozyme C P00699 LYSC_CALCC
96.9 Lysozyme C Q7LZQ0 LYSC_CATWA
96.9 Lysozyme C Q7LZP9 LYSC_LOPIM
96.1 Lysozyme C Q7LZI3 LYSC_TRASA
95.3 Lysozyme C P00701 LYSC_COTJA
96.1 Lysozyme C P19849 LYSC_PAVCR
95.3 Lysozyme C P22910 LYSC_CHRAM
95.3 Lysozyme C Q7LZT2 LYSC_TRATE
95.2 Lysozyme C P00703 LYSC_MELGA
92.2 Lysozyme C P00704 LYSC_NUMME
93.0 Lysozyme C P24364 LYSC_LOPLE
94.6 Lysozyme C P24533 LYSC_SYRRE
93.2 Lysozyme C P00702 LYSC_PHACO
93.0 Lysozyme C P81711 LYSC_SYRSO
92.3 Lysozyme C P49663 LYSC_PHAVE