[A new particle of chromatin obtained by proteolysis of histones with clostripain].

The proteolysis of the chromatin core particle by the arginine-specific endopeptidase clostripain yields a new nucleoprotein particle containing an unaltered DNA fragment of about 145 base pairs in length and a protein octameric core made up of twice the four histone fragments H2A, H2B, H3 and H4. This composition is suggested by the molecular weight of about 180 kd determined for the new particle by small angle neutron scattering. The histone fragments differ by about 2-3 kd each from the initial histones H2A, H2B, H3 and H4 and they correspond to the cleavage of the N-terminal part of the sequence (20-30 residues). A preliminary investigation by thermal denaturation, circular dichroism and small angle neutron scattering (measurement of a radius of gyration by the H2O-D2O contrast variation technique) indicates that the spatial organization of the new chromatin particle closely resembles that of the initial core particle.