PURIFICATION OF STREPTODORNASE FROM STREPTOCOCCUS-EQUISIMILIS AND ITSDNA-INDUCED CONFORMATIONAL CHANGE

Extracellular streptodornase was purified from fermentation media of S treptococcus equisimilis by stepwise carboxymethyl-Sepharose column ch romatography. The active enzyme fraction was eluted with phosphate buf fer containing 0.2 M NaCl. The purified enzyme showed a homogeneity on SDS-PAGE and had a subunit molecular weight of 35 kDa. Conformational change of streptodornase by binding to calf thymus DNA was examined b y circular dichroism (CD). CD study clearly showed a DNA-induced confo rmational change in the secondary structure of streptodornase, resulti ng in a decrease of alpha-helical content of the enzyme. (C) 1997 Acad emic Press