Abstract
The rate of dephosphorylation of isolated P-H2B histone by pig heart phosphoprotein phosphatase (Mr=224, 000) and its catalytic subunit (Mr=31, 000) was suppressed more than 95% at low ionic strength when the substrate was integrated into nucleosome core particles. The suppressed rate was increased 13-43-fold by polyamine hydrochlorides and Mg(CH3COO)2 at the optimal ionic strength of 0.2-0.38M. Phosphatase activity toward integrated P-H2B histone was distributed in both rat liver cytosol and nuclear extracts. The phosphatase activities in these fractions showed similar specific activities and were also increased 10-32-fold by 10mM spermine•4HCl.
