Regulation of synthesis of citrate synthase in regreening Euglena gracilis

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Abstract
Exposure of dark-grown Euglena to white or red light, but not blue light, produced a 2-fold increase in the specific activity of citrate synthase. A 400-fold purification of mitochondrial citrate synthase (subunit MW = 44,000) was achieved from cells of E. gracilis by affinity chromatography on ATP-activated agarose. Antisera, raised against the homogeneously pure enzyme, were used to demonstrate that the increase in citrate synthase activity on exposure of dark-grown cells to light resulted from an increase in citrate synthase protein. Anti-(citrate synthase) was used to detect precursor citrate synthase resulting from the translation of total polyadenylated RNA from Euglena in a cell-free rabbit reticulocyte lysate system. Citrate synthase mRNA was present in cells at all stages of regreening. Extraction and translation of polyadenylated RNA from free polysomes isolated from dark-grown and regreening cells demonstrated that appreciable translation of citrate synthase mRNA was only occurring in regreening cells.