Phosphate Transport in Biological Systems

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Inorganic phosphate and ATP are involved in more chemical reactions on the earth's surface than any other compound except water. Phosphate entry into eukaryotic cells and into their organelles is catalyzed by at least two distinct types of transport system, one, a Na+/P transporter and the other a H+/P transporter. Past work supported by NSF resulted in the identification of the H+/P transporter as a 32-35 kDa protein, its purification, reconstitution, cloning, sequencing, expression in E. coli, and import into isolated mitochondria. Future Specific Aims during the grant period are 6-fold and will be to. %%% Establish whether the functional form of the H+/Pi transporter in its native membrane environment is a monomer or a higher ordered oligomer. Express functionally the full length cDNA of the H+/Pi transporter and verify its membrane topology. Introduce both site directed and random mutations in the functionally expressed transporter in order to identify candidate amino acids involved in transport. Initiate studies which may prove valuable in supplying 3-Dimensional structural information about the H+/Pi transporter. Determine to what extent homologous H+/Pi transporters are expressed in plant and animal cells. Compare the regulatory events involved in the expression of H+/Pi transporter Gene(s) in plant and animal cells.