Abstract

In this thesis project, I undertook a study of the light regulation of a 46 kDa RNA binding protein associated with chloroplast membranes in C. reinhardtii . The optimal conditions for binding of this protein were characterized. Initial purification steps using (NH 4 ) 2 SO 4 precipitation and affinity chromatography revealed that this protein is present at extremely low abundance. This activity is low in the dark and increases drastically within 1-10 minute following a shift to light. This activation does not require protein synthesis in either the chloroplast or the cytosol. Finally activation is abolished by a proton ionophore and an inhibitor of the cytochrome b 6 /f complex, and partially reduced by an inhibitor of photosystem II. With a previous finding that ADP inhibits the RNA-binding activity of the protein in vitro , these results support a role of ADP in repression of this binding activity.