As a study on the ATP-inhibited ribonuclease of Bacillus subtilis the screening work for obtaining the ATP-inhibited ribonuclease negative mutant were carried out. And mutant strain was selected by the treatment of N-methyl-N´-nitro-N-nitrosoguanidine (NTG). For the selected strain the enzyme purification and some physiological properties were examined and the results obtained were as follows.
1. Among tested 1817 strains with the treatment of NTG, 101 strain was selected as a mutant strain.
2. ATP-inhibited ribonuclease was tentatively purified by several independent column chromatography. The results with Sephadex G-75 column were 30 times purification, 99% recovery, and 20 times purification, 98% recovery, respectively.
3. ATP-inhibited ribonuclease was purified by 60 times through acid treatment, ammonium fractionation, and two successive chromatography.
4. The purified ribonuclease were shown to be effectively concentrated in robonuclease content and to have reduced numbers of protein band on Disc electrophoresis.
5. This enzyme degraded single-stranded RNA to 2´, 3´-cyclic AMP, 2´, 3´-cyclic CMP, 2´, 3, -cyclic GMP, 2´, 3´-cyclic UMP and some unknown intermediates. The enzyme could not split double-stranded RNA.
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