title: Solute pores, ion channels, and metabolite transporters in the outer and inner envelope membranes of higher plant plastids.
abstract: All plant cells contain plastids. Various reactions are located exclusively within these unique organelles, requiring the controlled exchange of a wide range of solutes, ions, and metabolites. In recent years, several proteins involved in import and/or export of these compounds have been characterized using biochemical and electrophysiological approaches, and in addition have been identified at the molecular level. Several solute channels have been identified in the outer envelope membrane. These porin-like proteins in the outer envelope membrane were formerly thought to be quite unspecific, but have now been shown to exhibit significant substrate specificity and to be highly regulated. Therefore, the inter-envelope membrane space is not as freely accessible as previously thought. Transport proteins in the inner envelope membrane have been characterized in more detail. It has been proved unequivocally that a family of proteins (including triose phosphate-/phosphoenolpyruvate-, and glucose 6-phosphate-specific transporters) permit the exchange of inorganic phosphate and phosphorylated intermediates. A new type of plastidic 2-oxoglutarate/malate transporter has been identified and represents the first carrier with 12 putative transmembrane domains, to be located in the inner envelope membrane. The plastidic ATP/ADP transporter also contains 12 putative transmembrane domains and possesses striking structural similarity to ATP/ADP transporters found in intracellular, human pathogenic bacteria.
authors.affiliation: Pflanzenphysiologie, Universität Kaiserslautern, Postfach 3049, D-67653, Kaiserslautern, Germany. neuhaus@biologie.uni-osnabrueck.de
authors.forename: H E
authors.initials: HE
authors.lastname: Neuhaus
authors.forename: R
authors.initials: R
authors.lastname: Wagner
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D001692:Biological Transport; D002352:Carrier Proteins / Q000378:metabolism; D060365:Chloroplast Proteins; D002736:Chloroplasts / Q000378:metabolism; D007425:Intracellular Membranes / Q000378:metabolism*; D007473:Ion Channels / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D028044:Phosphate-Binding Proteins; D010940:Plant Proteins / Q000378:metabolism*; D018087:Plastids / Q000378:metabolism*; D018272:Porins / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D060365:Chloroplast Proteins; D007473:Ion Channels; D008565:Membrane Proteins; C113819:OEP24 protein, Pisum sativum; D028044:Phosphate-Binding Proteins; D010940:Plant Proteins; D018272:Porins; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate