L-arginyl-[protein] + NAD(+) = H(+) + N(omega)-(ADP-D-ribosyl)-L-arginyl-[protein] + nicotinamide Expressed in spleen and T-cells. DO is responsible for the Dombrock blood group system [MIM:616060]. The molecular basis of the Do(a)/Do(b) blood group antigen is a single variation in position 265; Asn-265 corresponds to Do(a) and Asp-265 to Do(b). It is also responsible for the antigens Gregory [Gy(a)], Holley [Hy] and Joseph [Jo(a)]. Belongs to the Arg-specific ADP-ribosyltransferase family. Blood group antigen gene mutation database