Sodium nitroprusside promotes NAD+ labelling of a 116 kDa protein in NG108-15 cell homogenates.

A 116 kDa protein in NG108-15 homogenates is labelled in the presence of [32P]NAD+. This protein was found to be poly(ADP-ribosyl)ated and appears to be a poly(ADP-ribosyl)transferase which has poly(ADP-ribosyl)ated itself. Sodium nitroprusside, an NO generating agent, also stimulates the labelling of this protein by [32P]NAD+, but this can only be seen in the presence of thymidine, which inhibits poly(ADP-ribosyl)transferase activity. Sodium nitroprusside also stimulates the labelling of this protein by [3H-nicotinamide]NAD+, indicating that NO facilitates the formation of an adduct between this protein and NAD+. The insensitivity of the linkage between the protein and NAD+ to mercuric ions indicates that the adduct does not involve thiol groups.