Author
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CHEN, LISCHEN - PLANT BIOLOGY UOFI URBANA |
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BUSH, DANIEL |
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Submitted to: Plant Physiology Supplement
Publication Type: Abstract Only Publication Acceptance Date: 7/31/1996 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: Although plants are photoautotrophic organisms, they contain many heterotrophic tissue systems that must import sugars and amino acids from primary sites of assimilation to support growth and development. This resource redistribution process is a fundamental activity that allows higher plants to function as multicellular organisms. Recently, our laboratory used functional complementation of yeast mutants as a novel approach to clone Arabidopsis amino acid transporters. In the results reported here, we've exploited the yeast expression system to extend our understanding of the molecular structure and function of these essential membrane proteins. Previous biochemical evidence implicated a histidine residue in the reaction mechanism of one of our amino acid transporters. Site-directed mutagenesis of a histidine residue located in a predicted trans-membrane domain identified that amino acid as an essential residue for transport function. In a complementary approach for identifying essential residues without prior experimental clues, we've also used random mutagenesis and transgenic expression in yeast to select mutant forms of the porter with altered substrate binding properties and coupling to the proton motive force. This was possible by designing screens that identify mutant forms of the transporter that exhibit altered transport properties. To date, we have five class of mutations that alter function. By mapping the location of specific residues that impact substrate binding and energy coupling, we are building a model of the folded porter in the membrane and are using that information to anchor our knowledge of transport mechanism and porter regulation. |
