Guanidine group specific ADP-ribosyltransferase in murine cells

We have identified a guanidine group specific ADP-ribosyltransferase activity, capable of transferring an ADP-ribose group from NAD to a low molecular weight guanidine compound p-(nitrobenzylidine)amino]guanidine and proteins such as histone and poly-L-arginine, in a variety of murine cell lines. The enzyme activity appears to be associated with an integral membrane protein of apparent molecular weight 30-33 kDa. Incubation of the viable cells in isotonic phosphate buffered saline with 32P]NAD results in the incorporation of label into cellular proteins. Dimethyl sulfoxide treatment of the cells downregulates the transferase activity as well as the ADP-ribosylation of cell proteins with extracellular NAD.