Involved in the regulation of nitrogen fixation activity by the reversible ADP-ribosylation of one subunit of the homodimeric dinitrogenase reductase component of the nitrogenase enzyme complex. The ADP-ribosyltransferase (DraT) transfers the ADP-ribose group from NAD to dinitrogenase reductase. The ADP-ribose group is removed through the action of the ADP-ribosylglycohydrolase (DraG, this entry). H2O + N(omega)-alpha-(ADP-D-ribosyl)-L-arginyl-[dinitrogen reductase] = ADP-D-ribose + L-arginyl-[dinitrogen reductase] Mn(2+) and Fe(2+) serve as a cofactor, Mg(2+) is a very poor cofactor (Ref.2). Binds 2 Mn(2+) per monomer, with unusually long metal coordination distances so that neither is tightly bound (PubMed:19706507). Monomer. Belongs to the ADP-ribosylglycohydrolase family.