The objective of this project is to learn more about the structure, function and regulation of enzymes in pea nuclei that are stimulated by phytochrome. Phytochrome stimulates the activity of nucleoside triphosphatase (NTPase) in purified pea nuclei, and calcium ions are necessary for this response. A calmodulin- dependent 47 kD NTPase has been isolated from pea nuclei and shown to have properties that implicate it as being the nuclear NTPase that is regulated by phytochrome. This NTPase appears to be closely related to a lamin-derived 46 kD NTPase in mammalian nuclei, whose activity is thought to be important for RNA export from nuclei. Additional sequence information on the plant NTPase will be obtained to confirm or disprove this relationship. There is some evidence that the phosphorylation of lamins in animal nuclei plays a critical role in its controlled degradation by proteolysis. The phosphorylation of the pea NTPase will be characterized, and its role both in the regulation of NTPase activity and in the production of NTPase from lamin-like precursors will be examined. The results should contribute to an improved understanding of how light can influence nuclear metabolism, with possible implications also for models of how light regulates plant gene expression.//
