Reversible Phosphorylation of Proteins in Volvox Carteri
Volvox carteri exhibit translational control of protein synthesis. Protein synthesis occurs in Volvox when they are exposed to light but not when the Volvox are in the dark. How protein synthesis is regulated is not known. My hypothesis is that reversible phosphorylation is involved in a cascade of reactions thereby regulating protein synthesis. By using biochemical techniques of 32p labeling of proteins, western blots, kinase assays and phosphatase assays, I attempted to visualize the phosphoproteins. I also attempted to assay the enzymes phosphorylating and dephosphorylating these proteins. There appear to be differences in the phosphoproteins of light and dark extracts, but the phosphoproteins containing phosphotyrosine are the same in both types of extracts. There seems to be more phosphatase activity occurring in the dark, and phosphatase activity under both light and dark conditions is increased by cGMP.