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.

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The complete primary structure of protein L2 which is the largest protein component of the E. coli 50 S subunit, has been established. A combination of enzymatic and chemical cleavages has been employed to isolate peptides, which were sequenced by the micro-DABITCYPITC double-coupling method [FEBS Lett. (1978) 93,205-2141. The sequence determined shows protein L2 to consist of 272 amino acid residues with M, = 29730. Secondary structure predictions were made based on the primary structure. Further, sequence regions homologous to other ribosomal proteins are presented. These results suggest protein L2, which binds specifically to the 23s RNA, to show homologous sequence stretches to the other RNA-binding proteins.

Osteocalcin was isolated from ovine (sheep) bone and purified by chromatography. The primary structure was determined using a manual micro‐DABITC/PITC double coupling method. Ovine osteocalcin contains two modified amino acids, 4‐hydroxyproline and γ‐carboxyglutamate. These residues were readily identified in the sequencing process and the data presented here extend the micro manual sequencing method to include identification of 4‐hydroxyproline and γ‐carboxyglutamate residues. Ovine osteocalcin consists of 49 amino acid residues and the sequence confirms the high degree of conservation previously observed between bovine and human osteocalcins.