Alternative targeting of Arabidopsis plastidic glucose 6-phosphate dehydogenase 1 (G6PD1) involves cysteine-dependent interaction with G6PD4 in the cytosol.
Summary of "Alternative targeting of Arabidopsis plastidic glucose 6-phosphate dehydogenase 1 (G6PD1) involves cysteine-dependent interaction with G6PD4 in the cytosol."
Arabidopsis peroxisomes contain an incomplete oxidative pentose-phosphate pathway (OPPP) consisting of 6-phospho-gluconoÔÇâlactonase and 6-phospho-gluconate dehydrogenase isoforms with peroxisomal targeting signals (PTS). To start the pathway, glucose-6-phosphate dehydrogenase (G6PD) is required, however G6PD isoforms with obvious C-terminal PTS1 or N-terminal PTS2 motifs are lacking. We used fluorescent reporter fusions to explore possibly hidden peroxisomal targeting information. Among the six Arabidopsis G6PD isoforms only plastid-predicted G6PD1 with free C-terminal end localized to peroxisomes. Detailed analyses identified SKY as internal PTS1-like signal, however, in a medial G6PD1 reporter fusion with free N- and C-terminal ends this cryptic information was overruled by the transit peptide. Yeast two-hybrid analyses revealed selective protein-protein interaction of G6PD1 with catalytically inactive G6PD4 and of both G6PD isoforms with plastid-destined thioredoxin m2 (Trx(m2) ). Serine replacement of redox-sensitive cysteines conserved in G6PD4 abolished the G6PD4-G6PD1 interaction, albeit analogous changes in G6PD1 did not. In planta-Bimolecular Fluorescence Complementation (BiFC) demonstrated that the G6PD4-G6PD1 interaction results in peroxisomal import. BiFC also confirmed interaction of Trx(m2) with G6PD4 (or G6PD1) in plastids, but co-expression analyses revealed Trx(m2) -mediated retention of medial G6PD4 (but not G6PD1) reporter fusions in the cytosol that was stabilized by CxxC(113) S exchange in Trx(m2) . Based on preliminary findings with plastid-predicted rice G6PD isoforms, we dismiss Arabidopsis G6PD4 as non-functional. G6PD4 orthologs (new P0 class) apparently evolved to become cytosolic redox switches that confer thioredoxin-relayed alternative targeting to peroxisomes.
Institut f├╝r Biologie und Biotechnologie der Pflanzen, Westf├Ąlische Wilhelms-Universit├Ąt M├╝nster, Schlossgarten 3, 48149 M├╝nster, Germany.
This article was published in the following journal.
Name: The Plant journal : for cell and molecular biology
- PubMed Source: http://www.ncbi.nlm.nih.gov/pubmed/21309870
- DOI: http://dx.doi.org/10.1111/j.1365-313X.2011.04535.x
Medical and Biotech [MESH] Definitions
Proteins that originate from plants species belonging to the genus ARABIDOPSIS. The most intensely studied species of Arabidopsis, Arabidopsis thaliana, is commonly used in laboratory experiments.
An ester of glucose with phosphoric acid, made in the course of glucose metabolism by mammalian and other cells. It is a normal constituent of resting muscle and probably is in constant equilibrium with fructose-6-phosphate. (Stedman, 26th ed)
An ATP-dependent enzyme that catalyzes the addition of ADP to alpha-D-glucose 1-phosphate to form ADP-glucose and diphosphate. The reaction is the rate-limiting reaction in prokaryotic GLYCOGEN and plant STARCH biosynthesis.
An enzyme that catalyzes the reversible interconversion of glucose 6-phosphate and fructose 6-phosphate, and is a part of the glycolytic and gluconeogenic pathways. Deficiency of the enzyme, an autosomal recessive trait, results in liver glycogenesis and hemolytic anemia. EC 18.104.22.168.
An enzyme that catalyzes the formation of UDPglucose from UTP plus glucose 1-phosphate. EC 22.214.171.124.
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