May have control over the extent of autophosphorylation of NRII (418) and indirectly over the phosphorylation of NRI. Phosphotransfer from NRII-phosphate to NRI. Phosphorylation of NRI can occur via two different physiological routes. The major route is a phosphotransfer from NRII-phosphate (NRII-P) (reaction II) (Table 6). Isolated NRII-P, free of ATP, phosphorylates NRI in the presence of Mg2 (1