Nuclease-T: an active derivative of staphylococcal nuclease composed of two noncovalently bonded peptide fragments.

An extracellular nuclease produced by Staphylococcus aureus1-3 has been shown to contain 149 amino acid residues (mol wt, 16,807) and to lack both sulfhydryl groups and disulfide bonds (Fig. 1).3-5 The enzyme catalyzes the cleavage of both DNA and RNA to yield 3’-nucleotides.2s 3 The absolute requirement for Ca++ l* 2s 6 may be explained by the interdependency of Gaff and nucleotide binding to the protein, and the conformation of the enzyme is stabilized by this reversible ligand int8eraction.‘* * The present communication summarizes experiments on the cleavage of the polypeptide chain by limit’ed digestion with trypsin in the presence of 3’,5’-deoxythymidine-diphosphate to yield three peptide fragments: Nase-T-PI9 (residues l-5), Nase-T-p2 (residues 6-49), and Nase-T-p, (residues 50149). The latter two fragments associate reversibly to form an active complex designated nuclease-T (Nase-T) which possesses approximately 8 per cent of the enzyme activity of the native enzyme.