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Ribonuclease from Streptomyces erythreus: Purification and properties

1971; Elsevier BV; Volume: 228; Issue: 3 Linguagem: Inglês

10.1016/0005-2787(71)90727-1

1879-3002

Nobuo Yoshida, Hideo Inoue, Atsushi Sasaki, Hideo Ōtsuka,

Protein purification and stability

Abstract Ribonuclease from Streptomyces erythreus has been purified by sequential chromatography with DEAE-cellulose, DEAE-Sephadex and QAE-Sephadex. The purified enzyme gives a simple band on polyacrylamide disc electrophoresis and an examination by sedimentation velocity indicates a high degree of homogeneity for the preparation. The purified ribonuclease has a sedimentation coefficient of 1.61 S, and a molecular weight of 11 900 as determined by a sedimentation equilibrium experiment is consistent with those estimated by gel filtration on Sephadex G-75 and from its amino acid composition. The isoelectric point was found to be around pH 4.5. The amino acid composition of the ribonuclease was determined. It shows a high proline content and contains two residues of half cystine corresponding to a single disulfide bond. Neither tryptophan nor methionine was found in the enzyme.