Studies on dinoflagellate chromosomal basic protein.

Routine cytochemical methods proved useless in demonstrating basic protein in dinoflagellate chromosomes because when the DNA was removed, these chromosomes dissolved away just as eubacterial nucleoids. However, with ammoniacal silver technique or alkaline Biebrich scarlet, DNA could be kept intact, all the dinoflagellate chromosomes examined gave positive reaction. The acid-soluble proteins were extracted from methanol-fixed Amphidinium carterae and methanol-fixed isolated nuclei of Noctiluca miliaris, and subjected to urea polyacrylamide gel electrophoresis. Only one band of basic protein co-migrating with histone H4 was found. The chromosomes of Oxyrrhis marina can retain their original forms after the removal of DNA. Their chromosomal basic protein can be demonstrated by various cytochemical methods. This protein co-migrates with histone H4 in urea gel too. Its amino acid composition has been determined. This protein can combine with DNA fibril to form a nucleosome-like structure which seems to be corresponding to two of the archaebacterial nucleosome-like structures and may represent the primitive nucleosome.