Identification of the three non-identical subunits constituting human deoxyribonuclease II

We purified DNase II from human liver to apparent homogeneity. The N-termin al amino acid sequences of each of three components constituting the purifi ed mature enzyme were then separately determined by automatic Edman degrada tion. A combination of this chemical information and the previously reporte d nucleotide sequence of the cDNA encoding human DNase II [Yasuda et al. (1 998) J. Biol. Chem. 273, 2610-2626] allowed detailed elucidation of the enz yme's subunit structure: human DNase II was composed of three non-identical subunits, a propeptide, proprotein and mature protein, following a signal peptide. Expression analysis of a series of deletion mutants derived from t he cDNA of DNase II in COS-7 cells suggested that although a single large p recursor protein may not be necessary for proteolytic maturation, the prope ptide region L-17-446 may play an essential role in generating the active f orm of the enzyme. (C) 1998 Federation of European Biochemical Societies.