Reassociation of deoxyribonuclease II with the lysosomal membrane isolated from porcine spleen.

DNase II, bound to the lysosomal membrane of porcine spleen, can be extracted from the membrane with 0.4 M NaCl. Reassociation of DNase II with the salt-extracted lysosomal membrane is readily accomplished in 0.01 M sodium acetate (pH 4.5). The reassociable amount of DNase II is approximately equal to the extractable amount. The capacity of the lysosomal membrane to bind DNase II is unaffected by the subtilisin treatment of the membrane. Phosphatidyl serine can bind DNase II as well, but with a much higher capacity. The erythrocyte plasma membrane on the other hand binds only about 20% of DNase II bound to the lysosomal membrane. The DNase II activity can be eluted from a column of the lysosomal membrane entrapped in 2% agarose and the elution pattern is very similar to that of CM-cellulose chromatography of DNase II, suggesting that electrostatic interactions may play an important role in the binding. The pH-reassociation profile is bell-shaped and is similar to the pH-activity profile of DNase II, having a maximum near pH 5. Under the nondenaturing condition, the dissociated alpha and beta subunits of DNase II cannot be reassociated to regain the enzymatic activity with or without the lysosomal membrane.