Phosphorylation of Very‐Lysine‐Rich Histone in <i>Physarum polycephalum</i>

Physarum polycephalum histones have been analysed by acrylamide gel electrophoresis. Two of the five major bands had electrophoretic mobilities identical with the mobilities of two bands from calf thymus histone. The P. polycephalum pattern is qualitatively the same at all stages of the synchronous mitotic cycle. Quantitative changes in the relative proportion and relative mobility of the very‐lysine‐rich histone are reported. In particular, a dramatic increase in phosphate content of this histone occurred in late G2 phase with a peak where chromosome condensation is seen to be occurring in the phase contrast microscope. Phosphate content is low during S phase and the peaks of RNA synthesis.