A method has been developed for the isolation of nuclei from the
flagellated protozoan Cuglena gracilis, and histone Isolated from the
nuclei has been extensively studied.
The amino acid composition of the unfractionated Euglena histone
is similar to that for the histone of higher organisms. Euglena
histone was separated by gel filtration into five fractions and the
individual fractions were further purified by selective precipitation
and solubility techniques. Amino acid analysis of the purified
proteins indicated the presence of f1, f2b, f2al and f3 histones.
The remaining fraction, designated f2a2, differed from vertebrate
f2a2 in having a higher lysinet arginino ratio. Polyacrylamide gel
electrophoresis in the presence of sodium dodecyl sulphate indicated
that the sizes of the individual Euglena histones are similar to the
homologous vertebrate fractions.
Using electrophoretic techniques, a comparison was made of
Euglena histone and histones isolated from rat liver, trypanosomatid
organisms and the colourless euglenold Astasia longa. The nature and
complexity of the histones from the various organisms were broadly
similar, but some differences in the electrophoretic patterns were