Effects of enzymatically digested microsome fractions on red-light-enhanced pelletability of pea phytochrome in vitro in the presence of calcium ion

摘要

The 130,000×g supernatant of Sephadex G-50 filtrate and a 78,000×g microsomal fraction were prepared separately from homogenates of etiolated pea (Pisum sativumL. cv. Alaska) shoots. The pelletability of phytochrome increased ca. 10-fold by exposure of the filtrate to red light and mixing the filtrate with the microsomal fraction in the dark at ca. 0°C. The increase of pelletable phytochrome was inhibited by 84%when the microsomal fraction digested with trypsin was used. Phospholipase C (Clostridium welchii) digestion of the microsome inhibited no more than 13%of the pelletability. Although phospholipase A2(Crotalus terrificus terrificus) digestion inhibited 43%of the pelletability, addition of defatted albumin during the enzymatic digestion completely restored the level of the pelletability. The decrease of RNA content of the microsomal fractions by ribonuclease A digestion did not result in a proportional inhibition of the pelletability. These results indicate that proteinaceous component in the microsomal fraction is essential for phytochrome pelletability in vitro, that RNA and polar heads of phospholipids are unlikely to be the partner for the binding, and that products of phospholipase A2digestion inhibit the pelletability partial