1. Front Cover.cdr - CORE

Session 6.Organelle biology
A B S T R A C T B O O K – A B S T R A C T S O F T A L K S
MOLECULAR IDENTIFICATION OF THE CHANNEL PROTEIN MEDIATING THE
DIFFUSION OF PHOTORESPIRATORY METABOLITES ACROSS THE
MEMBRANE OF PLANT PEROXISOMES
Pradeep Soni 1 , Elke Maier 2 , Roland Benz 2 , Sigrun Reumann 1
1 Centre for Organelle Research, University of Stavanger, Stavanger, Norway
2 Rudolf-Virchow-Zentrum, Wuerzburg, Germany
E-mail: pradeep.soni@uis.no
Plant peroxisomes are essential cell organelles that primarily carry out oxidative
metabolic reactions. Major metabolic pathways of plant peroxisomes such as
photorespiration have been described fairly well in the past years regarding the soluble
matrix proteins involved. However, transport proteins for metabolic intermediates have
not been identified in any plant species to date. Their identification and biochemical
characterization are highly important, for instance, to allow for kinetic modelling of
photorespiration under abiotic stress conditions. By electrophysiological means, a porinlike
channel has been characterized in the membrane of spinach leaf peroxisomes and
castor bean glyoxysomes in the 90s. To take advantage of the molecular and genomic
tools available for Arabidopsis, we isolated peroxisomes from mature Arabidopsis leaves.
Indeed, an anion-selective channel of similar single channel conductance could be
detected in a standard electrolyte such as 1 M KCl. The selectivity properties were
examined using different types of ions, and binding assays have been carried out using
different photorespiratory substrates. Taken together, the channel protein appears wellsuited
to mediate the diffusion of small carboxylates such as intermediates of
photorespiration, fatty acid beta-oxidation, and the glyoxylate cycle (C2-C6, e.g. glycolate,
malate, citrate). Candidate proteins including the Arabidopsis ortholog of a mammalian
metabolite channel of peroxisomes have been subcloned and are presently being overexpressed
in Pichia to allow for further purification by affinity chromatography. The
purified proteins will be reconstituted in planar lipid bilayers and their permeability
properties be investigated in different inorganic and organic ion solutions of different
structural properties.
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