Several different protocols have been developed to purify the ADP-ribosylating enzyme fromSulfolobus solfataricus. A number of techniques have been applied in regard to the crude homogenate preparation and protein extraction. Either mechanical cell lysis with DNAase digestion or freeze–thawing with sonication allowed to obtain fairly similar amounts of the thermozyme in the homogenate. While similar recovery of thermozyme was obtained by employing both purification protocols, the proteins were solubilized with different methods, and the affinity chromatography on NAD-Agarose of the first protocol was replaced by a gel filtration step in the second protocol. When enzyme activity was compared with electrophoresis and anti-poly-ADP-ribose polymerase 1 antibody immunoblotting results, it was noticed that lysis by sonication induces aggregation of monomeric PARP-like thermozyme at least in a dimeric form. The dimeric aggregate is also evidenced by treatment of cells with sonication followed by different protein extraction (Method III). Finally, we describe the third purification protocol that allows fast recovery of small amounts of purified ADP-ribosylating enzyme.
