Isolation of a 167 basepair chromatosome containing a partially digested histone H5.

A test has been made of the proposal that protection of the 167 basepair DNA length in the 'chromatosome' is due only to the central globular domain of the lysine-rich histones. Chicken erythrocyte chromatin was treated with trypsin to leave only the limit peptide from histones H1 and H5. Nucleosome monomers were then isolated on sucrose gradients following micrococcal nuclease digestion and were found to contain the 167 basepair DNA band as in intact chromatin. The presence of the limit peptide from H5 on the monomers was confirmed using an antibody to H5. It is concluded that the trypsin-susceptible domains of the lysine-rich histones are not involved in the protection of the 2-turn 167 basepair length of DNA in the nucleosome.