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-glucono lactonase 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.
Affiliation
Institut für Biologie und Biotechnologie der Pflanzen, Westfälische Wilhelms-Universität Münster, Schlossgarten 3, 48149 Münster, Germany.
Journal Details
This article was published in the following journal.
Name: The Plant journal : for cell and molecular biology
ISSN: 1365-313X
Pages:
Links
- 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
Arabidopsis Proteins
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.
Glucose-6-phosphate
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)
Glucose-1-phosphate Adenylyltransferase
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.
Glucose-6-phosphate Isomerase
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 5.3.1.9.
Utp-glucose-1-phosphate Uridylyltransferase
An enzyme that catalyzes the formation of UDPglucose from UTP plus glucose 1-phosphate. EC 2.7.7.9.
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