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Ionic strength dependent structural changes of nucleosomes
Acta Biologica Et Medica Germanica
|January 1, 1981
Summary
Nucleosome structure changes with salt concentration, involving histone release and conformational shifts. Ammonium sulfate solutions offer greater nucleosome stability compared to sodium chloride solutions.
Area of Science:
- Biochemistry
- Molecular Biology
- Structural Biology
Background:
- Nucleosomes are the fundamental structural units of eukaryotic DNA packaging.
- Understanding nucleosome stability and structural dynamics is crucial for comprehending DNA accessibility and gene regulation.
Purpose of the Study:
- To investigate the effects of varying ionic strengths on the sedimentation behavior and molecular weight of rat thymus nucleosomes.
- To elucidate the conformational changes and histone dissociation dynamics within nucleosomes under different salt conditions.
Main Methods:
- Sedimentation analysis in solutions of varying ionic strengths (NaCl and (NH4)2SO4).
- Molecular weight determination using sedimentation coefficients.
- Electrophoretic analysis to assess histone release.
- Calculation of molar frictional ratios to evaluate conformational changes.
Main Results:
- Nucleosome sedimentation coefficient (s20,w) and molecular weight (Mr) decreased in two distinct steps with increasing ionic strength.
- An additional decrease in Mr was observed between 0.005 and 0.4 ionic strength, attributed to histone release.
- Conformational changes were indicated by alterations in molar frictional ratios.
- Nucleosomes exhibited greater stability in ammonium sulfate solutions compared to sodium chloride solutions.
Conclusions:
- Nucleosome structure undergoes significant alterations, including histone dissociation and conformational changes, in response to increasing salt concentrations.
- The choice of salt (NaCl vs. (NH4)2SO4) influences nucleosome stability, with (NH4)2SO4 providing a more stabilizing environment.