Biochemical and functional characterization of histone H1-like proteins in procyclic <i>Trypanosoma brucei brucei</i>

Four variants and/or posttranslational modifications of histone H1-like proteins of <i>Trypanosoma brucei brucei</i> procyclic culture forms were extracted with 0.25N HCl from isolated nuclei and analyzed by two-dimensional gel electrophoresis. The amino acid composition of these proteins, their ability to space nucleosomes regularly and to induce salt-dependent condensation of the chromatin indicated their histone H1 nature. On the other hand, the histone H1-like proteins clearly differed from their higher-eukaryote counterparts by their weak interaction with DNA under low-salt conditions. As a consequence, intact nucleosome filaments were prepared according to a new preparation protocol especially adapted to the unstable chromatin of <i>T. b. brucei</i>. Our results indicate that the biochemical properties of the histone H1-like proteins contribute to the structural and functional differences between the chromatin of procyclic <i>T. b. brucei</i> and that of higher eukaryotes.