Crystallization from Calf Spleen of Two Inhibitors of Deoxyribonuclease I

The crystallization from calf spleen of two inhibitors of deoxyribonuclease I is reported in this paper. The inhibitors, protein in nature and designated I and II, were shown to act through the formation of stable complexes with DNase I and a method has been devised for the isolation of both complexes. The stoichiometry of complex formation was studied in detail in the case of Inhibitor II. It was found that the addition compound formed (mol wt 88,200) consisted of 1 mole of DNase I (mol wt 33,200) and 1 mole of Inhibitor II (mol wt 57,400).