Involved in the regulation of the nitrogen fixation activity by the reversible ADP-ribosylation of the 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). L-arginyl-[dinitrogen reductase] + NAD(+) = H(+) + N(omega)-alpha-(ADP-D-ribosyl)-L-arginyl-[dinitrogen reductase] + nicotinamide Optimum pH is 7.0. Monomer.