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Nonphosphorylating Glyceraldehyde-3-Phosphate Dehydrogenase Is Phosphorylated in Wheat Endosperm at Serine-404 by an SNF1-Related Protein Kinase Allosterically Inhibited by Ribose-5-Phosphate
Claudia Vanesa Piattoni, Diego Martín Bustos, Sergio Adrián Guerrero and Alberto Álvaro Iglesias
Vol. 156, No. 3 (July 2011), pp. 1337-1350
Published by: American Society of Plant Biologists (ASPB)
Stable URL: http://www.jstor.org/stable/41435043
Page Count: 14
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Nonphosphorylating glyceraldehyde-3-phosphate dehydrogenase (np-Ga3PDHase) is a cytosolic unconventional glycolytic enzyme of plant cells regulated by phosphorylation in heterotrophic tissues. After interaction with 14-3-3 proteins, the phosphorylated enzyme becomes less active and more sensitive to regulation by adenylates and inorganic pyrophosphate. Here, we acknowledge that in wheat (Triticum aestivum), np-GaSPDHase is specifically phosphorylated by the SnRK (SNF1-related) protein kinase family. Interestingly, only the kinase present in heterotrophic tissues (endosperm and shoots, but not in leaves) was found active. The specific SnRK partially purified from endosperm exhibited a requirement for Mg²⁺ or Mn²⁺ (being Ca²⁺ independent), having a molecular mass of approximately 200 kD. The kinase also phosphorylated standard peptides SAMS, AMARA, and SP46, as well as endogenous sucrose synthase, results suggesting that it could be a member of the SnRKl subfamily. Concurrently, the partially purified wheat SnRK was recognized by antibodies raised against a peptide conserved between SnRKls from sorghum (Sorghum bicolor) and maize (Zea mays) developing seeds. The wheat kinase was allosterically inhibited by ribose-5-phosphate and, to a lesser extent, by fructose-1,6-bisphosphate and 3-phosphoglycerate, while glucose-6-phosphate (the main effector of spinach [Spinacia olerácea] leaves, SnRKl) and trehalose-6-phosphate produced little or no effect. Results support a distinctive allosteric regulation of SnRKl present in photosynthetic or heterotrophic plant tissues. After in silico analysis, we constructed two np-Ga3PDHase mutants, S404A and S447A, identifying serine-404 as the target of phosphorylation. Results suggest that both np-Ga3PDHase and the specific kinase could be under control, critically affecting the metabolic scenario involving carbohydrates and reducing power partition and storage in heterotrophic plant cells.
Plant Physiology © 2011 American Society of Plant Biologists (ASPB)