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Isolation and characterization of histones and other acid-soluble chromosomal proteins from Physarum polycephalum
Abstract:
Chromosomal basic proteins were isolated from amoebal and plasmodial stages of the acellular slime mold Physarum polycephalum. Polyacrylamide electrophoresis on high resolution acid-urea gels separated the five histone fractions in the sequence H1, H2A, H2B, H3, and H4. Under these electrophoretic conditions Physarum histones migrated more like plant (rye) than animal (calf) histones. Furthermore, Physarum histones H1, H2A, and H2B have higher molecular weights on sodium dodecyl sulfate (SDS) gels than the corresponding calf fractions. No differences were detected between amoebal and plasmodial histones on either acid-urea or SDS-polyacrylamide gel electrophoresis. Amoebal basic proteins were fractionated by exclusion chromatography. The five histone fractions plus another major acid-soluble chromosomal protein (AS) were isolated. The Physarum core histones had amino acid compositions more closely resembling those of the calf core histones than of rye, yeast, or Dictyostelium. Although generally similar in composition to the plant and animal H1 histones, the Physarum H1 had a lower lysine content. The AS protein was extracted with 5% perchloric acid or 0.5 M NaCl, migrated between histones H3 and H4 on acid-urea polyacrylamide gels, and had an apparent molecular weight of 15 900 on SDS gels. It may be related to a protein migrating near H1. Both somewhat resembled the high mobility group proteins in amino acid composition.
Insights
Physarum polycephalum histones, including H1, H2A, H2B, H3, and H4, were analyzed. Physarum histones exhibit characteristics similar to plant histones but share amino acid compositions closer to animal core histones.
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- Acellular slime molds like Physarum polycephalum offer a unique model for studying fundamental cellular processes.
- Understanding chromosomal basic proteins, particularly histones, is crucial for comprehending gene regulation and chromatin structure.
Purpose of the Study:
- To isolate and characterize the histone fractions from both amoebal and plasmodial stages of Physarum polycephalum.
- To compare the electrophoretic and compositional properties of Physarum histones with those of other species, including plants and animals.
Main Methods:
- High-resolution acid-urea polyacrylamide gel electrophoresis for histone separation.
- Sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis for molecular weight determination.
- Exclusion chromatography for fractionating amoebal basic proteins.
- Amino acid composition analysis.
Main Results:
- Five distinct histone fractions (H1, H2A, H2B, H3, H4) were identified in Physarum polycephalum.
- Physarum histones displayed electrophoretic migration patterns more akin to plant histones than animal histones.
- Physarum core histones showed amino acid compositions similar to calf core histones, while H1 histone had lower lysine content.
- An additional acid-soluble (AS) protein, potentially related to high mobility group proteins, was identified.
Conclusions:
- Physarum polycephalum histones share characteristics with both plant and animal histones, suggesting evolutionary conservation and divergence.
- The identified AS protein represents a novel chromosomal component in Physarum, warranting further investigation.
- No significant differences were observed in histone profiles between the amoebal and plasmodial stages, indicating conserved chromatin structure.