Nucleosome core histone complex isolated gently and rapidly in 2 M NaCl is octameric

Abstract

A relatively stable specific complex of the chromatin core histones H2A, H2B, H3, and H4 has been obtained in 2 M NaCl/25 mM sodium phosphate buffer, pH 7.0. The histone core complex has an apparent specific volume of 0.73 ml/g. Its sedimentation coefficient was dependent on rotor speed (angular velocity, omega) and attained different stable values at low and high rotor speeds. The drop in sedimentation coefficient occurred sharply between omega 2 values of about 9 × 10⁶ and 1.1 × 10⁷ (radians/sec)². The s020,w corresponding to zero angular velocity (1 atmosphere pressure) was 6.6 S ± (SEM) 0.1 S. At high rotor speeds the value decreased to 3.8 S ± 0.1 S. The core complex has a diffusion coefficient, D20,w, of 5.4 × 10^-7 cm²/sec and a molecular weight of 108,000 ± (SD) 2500.