[Theoretical study of structural transition in a nucleosome at low ionic strength].
The theoretical analysis of nucleosome stability at low ionic strength has been performed on the basis of consideration of different contributions to the free energy of compact state of the nucleosome DNA terminal regions. The proposed model explains: the fact of low-salt structural change; the transition point (approximately 1.7 mM NaCl) and width (approximately 1 mM); the shift of the transition to the higher salt concentrations in the case of histones tails removal by trypsin. According to the model the increase of electrostatic repulsion between neighbouring turns of DNA superhelix is the main cause of the unwinding of nucleosomal DNA terminal regions in the course of low-salt structural change. The interactions between histone (H2A-H2B) dimer and (H3-H4)2 tetramer provide the compact state of the nucleosomal DNA terminal regions. The existence of electrostatic interactions of nucleosomal DNA terminal regions with tetramer was suggested. These interactions can provide the compact state of nucleosomal DNA at physiological ionic strength even in the absence of (H2A-H2B) dimer.
Sivolob
A V
AV
Dragan
A I
AI
Khrapunov
S N
SN
D004247:DNA; D006657:Histones; D008962:Models, Theoretical; D009690:Nucleic Acid Conformation; D009707:Nucleosomes; D009994:Osmolar Concentration
D006657:Histones; D009707:Nucleosomes; D004247:DNA
Teoreticheskoe issledovanie strukturnogo perekhoda v nukleosome pri nizkoĭ ionnoĭ sile.