Biopolymers and cell. 1987. Volume 3. № 4. 192 - 201

A. V, Sivolob, S. N. Khrapunov

THE STRUCTURE OF HISTONE OCTAMER IN THE COMPOSITION OF RECONSTITUTED POLYNUCLEOSOMES IN PRESENCE OF HI HISTONE AND DIVALENT CATIONS

Summary

    The influence of HI histone and divalent cations upon the structure of (H2A-H2B-H3-H4)2 histone octamer in the complex with high-molecular weight DNA has been studied by fluorescence spectroscopy. Changes in the position of tyrosine histone fluorescence spectrum indicate the existence of three structural states of octamer in the nucleosorne without HI histone: «expanded» octamer (I) within 30-600 mM NaCl; «compact» octamer (II) within 3-20 mM NaCl; «unfolded» octamer (III) within less than 1 mM NaCl. Cation agents of different nature (Na+, Ca2+, Mg2+ ions, HI histone), acting either independently or in combination exert a similar effect upon structural rearrangements of nucleosorne. The obtained results permit concluding that histone octamer structure in 2 M NaCl is similar to that in disordered nucleosome fiber, but it considerably differs from the octamer state within the compact chromatin.