Isolation by preparative electrophoresis and characterization of histone P3 from the slime mold Physarum polycephalum

Isolation, identification, and characterization of histones from plasmodia of the true slime mold Physarum polycephalum using extraction with guanidine hydrochloride

Histones from plasmodia of the true slime mold Physarum polycephalum have been prepared free of slime by an approach to histone isolation that uses extraction of nuclei with 40% guanidine hydrochloride and chromatography of the extract on Bio-Rex 70. This procedure followed by chromatography or electrophoresis has been used to obtain pure fractions of histones from Physarum microplasmodia. Physarum microplasmodia have five major histone fractions, and we show by amino acid analysis, apparent molecular weight on three gel systems containing sodium dodecyl sulfate, mobility on gels containing Triton X-100, and other characterizations that these fractions are analogous to mammalian histones H1, H2A, H2B, H3, and H4. Significant differences between Physarum and mammalian histones are noted, with histone H1 showing by far the greatest variation. Histones H1 and H4 from Physarum microplasmodia have similar, but not identical, products of partial chymotryptic digestion compared with those of calf thymus histones H1 and H4. Labeling experiments, in vivo, showed that histone H1 is the major phosphorylated histone and approximately 15 separate phosphopeptides are present in a tryptic digest of Physarum histone H1. The core histones from Physarum, histones H2A, H2B, H3, and H4, are rapidly acetylated; histone H4 shows five subfractions, analogous to the five subfractions of mammalian histone H4 (containing zero to four acetyllysine residues per molecule); histone H3 has a more complex pattern that we interpret as zero to four acetyllysine residues on each of two sequence variants of histone H3; histones H2A and H2B show less heterogeneity. Overall, the data show that Physarum microplasmodia have a set of histones that is closely analogous to mammalian histones.

The core histones from the slime mold Physarum polycephalum. Isolation and characterization

The histones of Physarum polycephalum have been isolated and fractionated using a combination of gel exclusion and ion-exchange chromatography or differential precipitation. The four core histones were unambiguously identified by gel electrophoresis, amino acid composition and N-terminal analysis. The molecular weight of Physarum histones H3, H2B and H4 are very close or identical to the corresponding histones from chicken erythrocytes. Physarum H2A is significantly larger than chicken erythrocyte H2A and its N-terminal residue is alanine. From the differences in amino acid compositions and in the peptide maps between Physarum and calf H4, one can expected some changes in the amino acid sequence of Physarum H4.