Widell S, Sommarin M
Purification of Endoplasmic-Reticulum from Wheat Roots and Shoots (Triticum-Aestivum) - Comparison of Their Blue Light-Sensitive Redox Components with Those of Highly Purified Plasma-Membrane
Physiologia Plantarum: 1991 82:9-18
Plasma membranes (PM) and endoplasmic reticulum (ER) were prepared from 4.5-day-old, light-grown wheat (Triticum aestivum L. cv. Drabant) shoots and roots, using phase partitioning for the PM, which yields very pure PM preparations, and sucrose gradient centrifugation for the ER. Also the ER fractions were highly purified, being totally free from mitochondria (cytochrome c oxidase, EC 18.104.22.168), PM (glucan synthase II, EC 22.214.171.124) and thylakoid membranes (chlorophyll), and with a low content of tonoplast (nitrate-sensitive ATPase) and Golgi (latent IDPase). Sodium dodecyl sulphate polyacrylamide gel electrophoresis of root ER resulted in a similar polypeptide pattern as for shoot ER, but very different from the crude fraction from which the ER fractions were purified, also indicative of a high purity. The PM and ER preparations were compared with respect to their blue light-sensitive flavoprotein-cytochrome b. About half of the dithionite-reducible cytochrome b of shoots (PM as well as ER) and root PM was light-sensitive, compared to only 10-20% of that of root ER. Shoot PM needed 2-3 times less light compared to the other membranes, for half saturation of the reaction. NADH-cytochrome c reductase activity was found with all four membrane fractions, with ER having activities 5-10 times higher than PM. The relevance of photoreducible components in the PM and the ER is discussed in connection with blue light photobiology.
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