Enzymatic unpacking of bull sperm chromatin.

When isolated bull sperm chromatin is incubated with 0.1 M 2-mercaptoethanol at pH 8, an extensive proteolytic degradation of sperm histone occurs, being accompanied by a marked swelling of the chromatin masses. The degradation of sperm histone is strongly inhibited by monovalent or divalent metal ions. The protease found in isolated bull sperm chromatin possesses properties indistinguishable from those of an acrosomal protease of trypsin-type, acrosin (EC 3.4.21.10), and requires a combination of NaCl, urea and 2-mercaptoethanol for its extraction. Evidence suggests that the protease travels along chromatin strands and hydrolyzes essentially all the sperm histone molecules within the chromatin masses.