This proposal is looking at the regulation of synthesis of LHCPII at the level of translational control in Euglena. Both genomic and cDNA clones of Euglena LHCPII are being sequenced to determine the identity of the proteins derived from a polyprotein intermediate found during LHCPII synthesis. LHCPII mRNA levels and the recruitment of LHCPII mRNA into polysomes are measured to determine whether translational control operates at the level of initiation of translation or afterwards. Hybrid-release and - arrest studies are being used to determine the extent to which all four preLHCPIIs are derived through internal initiation of the polyprotein mRNA. The results of these studies will aid in understanding the mechanisms of light regulation of LHCPII translation in Euglena. This proposal looks at the light regulation of protein synthesis of the photosynthetic protein LHCPII in the unicellular organism Euglena. This alga shows an unusual pattern of regulation of this protein such that synthesis of the mRNA is held constant and the light-induced increase in LHCPII protein is associated with an increased level of translation of the mRNA to protein. The research outlined in this proposal is looking at the mechanism by which this translational control is achieved since the light regulation of LHCPII in other photosynthetic organisms operates at the level of mRNA production, not translation. The results of this research should provide new insights into the mechanisms of translational control in higher organisms, both plant and animal.
