BIOCHEMICAL AND FUNCTIONAL-CHARACTERIZATION OF HISTONE H1-LIKE PROTEINS IN PROCYCLIC TRYPANOSOMA-BRUCEI-BRUCEI

Four variants and/or posttranslational modifications of histone H1-lik e proteins of Trypanosoma brucei brucei procyclic culture forms were e xtracted with 0.25 N HCl from isolated nuclei and analyzed by two-dime nsional gel electrophoresis. The amino acid composition of these prote ins, their ability to space nucleosomes regularly and to induce salt-d ependent condensation of the chromatin indicated their histone H1 natu re. On the other hand, the histone H1-like proteins clearly differed f rom their higher-eukaryote counterparts by their weak interaction with DNA under low-salt conditions. As a consequence, intact nucleosome fi laments were prepared according to a new preparation protocol especial ly adapted to the unstable chromatin of T. b. brucei. Our results indi cate that the biochemical properties of the histone H1-like proteins c ontribute to the structural and functional differences between the chr omatin of procyclic T. b. brucei and that of higher eukaryotes.