Site‐specific regulatory interaction between spinach leaf sucrose‐phosphate synthase and 14‐3‐3 proteins

Abstract

We report an Mg 2+ -dependent interaction between spinach leaf sucrose-phosphate synthase (SPS) and endogenous 14-3-3 proteins, as evidenced by co-elution during gel filtration and co-immunoprecipitation. The content of 14-3-3s associated with an SPS immunoprecipitate was inversely related to activity, and was specifically reduced when tissue was pretreated with 5-aminoimidazole-4-carboxamide riboside, suggesting metabolite control in vivo. A synthetic phosphopeptide based on Ser-229 was shown by surface plasmon resonance to bind a recombinant plant 14-3-3, and addition of the phosphorylated SPS-229 peptide was found to stimulate the SPS activity of an SPS:14-3-3 complex. Taken together, the results suggest a regulatory interaction of 14-3-3 proteins with Ser-229 of SPS.z 1998 Federation of European Biochemical Societies.

Regulation of starch accumulation by granule-associated plant 14-3-3 proteins

“…While we cannot rule out a contributory role in starch accumulation by cytosolic and͞or other upstream enzymatic perturbations caused by reduction of 14-3-3 proteins (27,28), a direct role of in plastid 14-3-3 proteins in regulation of starch accumulation is clearly indicated. Additionally, the increase in branched glucans vs. nonbranched glucans in the antisense plants would seem contrary to simply increasing the cytosolic flux of starch precursors, as would be the effect of altered upstream regulation of starch metabolism.…”

Data Mining the Arabidopsis Genome Reveals Fifteen 14-3-3 Genes. Expression Is Demonstrated for Two out of Five Novel Genes

“…In particular, plant 14-3-3s have been found to be important regulators of primary metabolism. For example, nitrate reductase and Suc phosphate synthase, which are key enzymes in nitrogen and carbon metabolism, respectively, are both inhibited by binding of 14-3-3 (Bachmann et al, 1996;Moorhead et al, 1996;Toroser et al, 1998), whereas binding of 14-3-3 to the plasma membrane H ϩ ATPase activates H ϩ pumping (Jahn et al, 1997;Oecking et al, 1997) and hence stimulates nutrient uptake.…”

Phosphorylation of Thr-948 at the C Terminus of the Plasma Membrane H+-ATPase Creates a Binding Site for the Regulatory 14-3-3 Protein

“…Approximately half of the 14-3-3-interacting proteins contain the motif RSXpSXP (where X stands for any amino acid and p denotes a phosphorylated amino acid; Muslin et al, 1996), and others contain a similar motif, RXY/FXpSP (Yaffe et al, 1997). However, several 14-3-3 binding proteins do not have any of these conserved motifs, and some have nonphosphorylated motifs (Du et al, 1996;Petosa et al, 1998).In plants, enzymes shown to bind 14-3-3 proteins include nitrate reductase (Bachmann et al, 1996;Moorhead et al, 1996), sucrose-phosphate synthase (Toroser et al, 1998), and the plasma membrane H ϩ -ATPase (Jahn et al, 1997;Oecking et al, 1997). With nitrate reductase and sucrosephosphate synthase, binding of 14-3-3 protein involves phosphorylated motifs similar to that described by Muslin et al (1996); 14-3-3 binding to these enzymes results in inhibition of activity (Bachmann et al, 1996;Moorhead et al, 1996;Toroser et al, 1998).…”