Protein phosphorylation in isolated nuclei from etiolated Avena seedlings. Effects of red/far-red light and cholera toxin

We have studied the phosphorylation/dephosphorylation of several nuclear proteins in isolated nuclei from etiolated Avena seedlings as a function of red/far-red light. The effect of stimulatory (ADP-ribosylation by cholera toxin) or inhibitory (GDP beta S) conditions for GTP-binding proteins was also studied. Red or far-red light enhanced the phosphorylation level of 2 nuclear proteins with molecular masses of 75 and 60 kDa. The phosphorylation pattern was affected by the addition of cholera toxin or GDP beta S to the isolated nuclei. At least 2 proteins with molecular masses of 24 and 75 kDa cross-reacted by Western blot with GTP-binding protein antibodies.