The chloroplast phosphate-translocator catalyzes the exchange of three-carbon organic phosphate compounds and inorganic phosphate in both C3 and C4 plants. A major difference between the two photosynthetic types is the transport of phosphoenolpyruvate by the C4 translocator. This process is essential for C4 photosynthesis to operate. The long term objective of this proposal is to characterize the evolutionary changes and the molecular organization of the Pi translocator protein in the chloroplasts and to elucidate its structure/function relationship. The specific objectives include the direct measurement of PEP transport in isolated chlroplasts by silicone oil centrifugation, microautoradiography and immunofluorescence and purification of the translocator using affinity chromatography and non- permeant covalent probes combined with limited proteolysis. The results will enhance our knowledge of ion transport in plant and animal cells, and may provide a potential target for genetic improvement of crops.
