ISOLATION OF NUCLEAR HISTONES FROM MYXOMYCETE, PHYSARUM POLYCEPHALUM

A method has been developed for the extraction of nuclear histones with 1 m CaCl2. The new procedure gave a much higher yield of histone from nuclei of Physarum polycephalum than could be obtained with the conventional mineral acid and salt extractions, and the histone preparation had a more reproducible electrophoretic pattern. Calcium chloride gave the same yields and electrophoretic patterns as mineral acids and NaCl when used with calf thymus and chick erythrocyte nuclei. Physarum nuclei contained equal amounts of histone and DNA, on a weight basis. The histone was fractionated by electrophoresis at pH 4.3 in polyacrylamide into seven characteristic bands-three large bands and one small band with higher mobility, and three smaller bands with lower mobility. The electrophoretic pattern was very similar to that of calf thymus histone and in coelectrophoresis five bands moved with thymus histones. Two of the major bands migrated with lysine-rich and arginine-rich thymus histones. The largest Physarum fraction migrated slightly slower than moderately lysine-rich histone. Physarum histone also contained about 10% of a lysine-rich band not occurring in thymus. Dye-binding capacities of the Physarum histone bands have been determined, and the arginine-rich bands were found to bind up to twice as much amido black 10B as the lysine-rich bands. The amino acid compositions of three lysine-rich components have been determined. All had compositions distinct from thymus fractions, but one, the largest band in Physarum histone, resembled moderately lysine-rich histone; and another, the band unique to Physarum, resembled very lysine-rich histone. © 1969.