Thermodynamic studies of the core histones: Ionic strength and pH dependence of H2A-H2B dimer stability

Vassiliki Karantza, Ernesto I Freire, Ernesto Freire, Evangelos N. Moudrianakis

Research output: Contribution to journalArticle

Abstract

The thermal stability of the core histone dimer H2A-H2B has been studied by high-sensitivity differential scanning calorimetry and circular dichroism spectroscopy. The unfolding transition temperature of the 28 kDa H2A-H2B dimer increases as a function of both the ionic strength of the solvent and the total protein concentration. At neutral pH and physiological ionic strength, the thermal denaturation is centered at about 50°C with a corresponding enthalpy change of about 40 kcal/mol of 14 kDa monomer unit and an excess heat capacity of about 1.4 kcal/(K·mol) of 14 kDa monomer unit. The H2A-H2B dimer is stable mainly between pH 5.5 and 10.5. Below pH 4.0, the system is unfolded at all temperatures. The thermodynamic analysis is performed at low ionic strength where almost complete reversibility is attained, since higher salt conditions seem to promote aggregation and irreversibility of the transitions. Analysis of the data shows that at low ionic strength and pH values between 6.5 and 8.5, the H2A-H2B dimer behaves as a highly cooperative system, melting as a single unit without any detectable intermediates of dissociated, yet folded, H2A and H2B monomers. This is consistent with the observed protein concentration dependence of the midpoint of the thermal denaturation. The two-state unfolding process can be described by the general scheme AB → 2U, indicating that the individual H2A and H2B polypeptides are folded, stable entities only when complexed as the H2A-H2B dimer and that the major contribution to the stabilization of the dimer derives from the coupling between the H2A and H2B interfaces.

Original languageEnglish (US)
Pages (from-to)5988-5996
Number of pages9
JournalBiochemistry®
Volume34
Issue number17
StatePublished - 1995

Fingerprint

Ionic strength
Thermodynamics
Dimers
Histones
Osmolar Concentration
Hot Temperature
Denaturation
Monomers
Transition Temperature
Differential Scanning Calorimetry
Circular Dichroism
Freezing
Circular dichroism spectroscopy
Spectrum Analysis
Proteins
Salts
Peptides
Temperature
Specific heat
Differential scanning calorimetry

ASJC Scopus subject areas

  • Biochemistry

Cite this

Thermodynamic studies of the core histones : Ionic strength and pH dependence of H2A-H2B dimer stability. / Karantza, Vassiliki; Freire, Ernesto I; Freire, Ernesto; Moudrianakis, Evangelos N.

In: Biochemistry®, Vol. 34, No. 17, 1995, p. 5988-5996.

Research output: Contribution to journalArticle

Karantza, Vassiliki ; Freire, Ernesto I ; Freire, Ernesto ; Moudrianakis, Evangelos N. / Thermodynamic studies of the core histones : Ionic strength and pH dependence of H2A-H2B dimer stability. In: Biochemistry®. 1995 ; Vol. 34, No. 17. pp. 5988-5996.
@article{2c546b1b80024018ba3934af634b5084,
title = "Thermodynamic studies of the core histones: Ionic strength and pH dependence of H2A-H2B dimer stability",
abstract = "The thermal stability of the core histone dimer H2A-H2B has been studied by high-sensitivity differential scanning calorimetry and circular dichroism spectroscopy. The unfolding transition temperature of the 28 kDa H2A-H2B dimer increases as a function of both the ionic strength of the solvent and the total protein concentration. At neutral pH and physiological ionic strength, the thermal denaturation is centered at about 50°C with a corresponding enthalpy change of about 40 kcal/mol of 14 kDa monomer unit and an excess heat capacity of about 1.4 kcal/(K·mol) of 14 kDa monomer unit. The H2A-H2B dimer is stable mainly between pH 5.5 and 10.5. Below pH 4.0, the system is unfolded at all temperatures. The thermodynamic analysis is performed at low ionic strength where almost complete reversibility is attained, since higher salt conditions seem to promote aggregation and irreversibility of the transitions. Analysis of the data shows that at low ionic strength and pH values between 6.5 and 8.5, the H2A-H2B dimer behaves as a highly cooperative system, melting as a single unit without any detectable intermediates of dissociated, yet folded, H2A and H2B monomers. This is consistent with the observed protein concentration dependence of the midpoint of the thermal denaturation. The two-state unfolding process can be described by the general scheme AB → 2U, indicating that the individual H2A and H2B polypeptides are folded, stable entities only when complexed as the H2A-H2B dimer and that the major contribution to the stabilization of the dimer derives from the coupling between the H2A and H2B interfaces.",
author = "Vassiliki Karantza and Freire, {Ernesto I} and Ernesto Freire and Moudrianakis, {Evangelos N.}",
year = "1995",
language = "English (US)",
volume = "34",
pages = "5988--5996",
journal = "Biochemistry",
issn = "0006-2960",
publisher = "American Chemical Society",
number = "17",

}

TY - JOUR

T1 - Thermodynamic studies of the core histones

T2 - Ionic strength and pH dependence of H2A-H2B dimer stability

AU - Karantza, Vassiliki

AU - Freire, Ernesto I

AU - Freire, Ernesto

AU - Moudrianakis, Evangelos N.

PY - 1995

Y1 - 1995

N2 - The thermal stability of the core histone dimer H2A-H2B has been studied by high-sensitivity differential scanning calorimetry and circular dichroism spectroscopy. The unfolding transition temperature of the 28 kDa H2A-H2B dimer increases as a function of both the ionic strength of the solvent and the total protein concentration. At neutral pH and physiological ionic strength, the thermal denaturation is centered at about 50°C with a corresponding enthalpy change of about 40 kcal/mol of 14 kDa monomer unit and an excess heat capacity of about 1.4 kcal/(K·mol) of 14 kDa monomer unit. The H2A-H2B dimer is stable mainly between pH 5.5 and 10.5. Below pH 4.0, the system is unfolded at all temperatures. The thermodynamic analysis is performed at low ionic strength where almost complete reversibility is attained, since higher salt conditions seem to promote aggregation and irreversibility of the transitions. Analysis of the data shows that at low ionic strength and pH values between 6.5 and 8.5, the H2A-H2B dimer behaves as a highly cooperative system, melting as a single unit without any detectable intermediates of dissociated, yet folded, H2A and H2B monomers. This is consistent with the observed protein concentration dependence of the midpoint of the thermal denaturation. The two-state unfolding process can be described by the general scheme AB → 2U, indicating that the individual H2A and H2B polypeptides are folded, stable entities only when complexed as the H2A-H2B dimer and that the major contribution to the stabilization of the dimer derives from the coupling between the H2A and H2B interfaces.

AB - The thermal stability of the core histone dimer H2A-H2B has been studied by high-sensitivity differential scanning calorimetry and circular dichroism spectroscopy. The unfolding transition temperature of the 28 kDa H2A-H2B dimer increases as a function of both the ionic strength of the solvent and the total protein concentration. At neutral pH and physiological ionic strength, the thermal denaturation is centered at about 50°C with a corresponding enthalpy change of about 40 kcal/mol of 14 kDa monomer unit and an excess heat capacity of about 1.4 kcal/(K·mol) of 14 kDa monomer unit. The H2A-H2B dimer is stable mainly between pH 5.5 and 10.5. Below pH 4.0, the system is unfolded at all temperatures. The thermodynamic analysis is performed at low ionic strength where almost complete reversibility is attained, since higher salt conditions seem to promote aggregation and irreversibility of the transitions. Analysis of the data shows that at low ionic strength and pH values between 6.5 and 8.5, the H2A-H2B dimer behaves as a highly cooperative system, melting as a single unit without any detectable intermediates of dissociated, yet folded, H2A and H2B monomers. This is consistent with the observed protein concentration dependence of the midpoint of the thermal denaturation. The two-state unfolding process can be described by the general scheme AB → 2U, indicating that the individual H2A and H2B polypeptides are folded, stable entities only when complexed as the H2A-H2B dimer and that the major contribution to the stabilization of the dimer derives from the coupling between the H2A and H2B interfaces.

UR - http://www.scopus.com/inward/record.url?scp=0029053420&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0029053420&partnerID=8YFLogxK

M3 - Article

C2 - 7727455

AN - SCOPUS:0029053420

VL - 34

SP - 5988

EP - 5996

JO - Biochemistry

JF - Biochemistry

SN - 0006-2960

IS - 17

ER -