Figure 4: Schematic diagram of the HNP-1 ADP-ribosylation. The picture shows that ART1 catalyzes the transfer of an ADP-ribose unit from NAD to HNP-1 on Arg14 with simultaneous release of nicotinamide (NAM) in the extracellular space. ART1 is anchored via a GPI tail to the outer leaflet of the cell membrane.