Phosphorylation of Serine-15 of Maize Leaf Sucrose Synthase (Occurrence in Vivo and Possible Regulatory Significance)
| Autor: | P. C. Liao, Robert W. McMichael, Douglas A. Gage, Steven C. Huber, Karen E. Koch, Prem S. Chourey, L. C. Hannah, Joan L. Huber |
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| Rok vydání: | 1996 |
| Předmět: |
inorganic chemicals
Phosphopeptides Physiology Protein subunit Molecular Sequence Data Peptide Plant Science Protein Serine-Threonine Kinases Biology environment and public health Peptide Mapping Zea mays Gene Expression Regulation Enzymologic Serine Genetics Protein phosphorylation Amino Acid Sequence Phosphorylation Protein kinase A Conserved Sequence Plant Proteins chemistry.chemical_classification Edman degradation Isoenzymes Plant Leaves enzymes and coenzymes (carbohydrates) chemistry Biochemistry Glucosyltransferases Spectrometry Mass Matrix-Assisted Laser Desorption-Ionization biology.protein bacteria Sucrose synthase Oligopeptides Protein Kinases Sequence Analysis Research Article |
| Zdroj: | Plant Physiology. 112:793-802 |
| ISSN: | 1532-2548 0032-0889 |
| Popis: | Experiments were conducted to determine whether sucrose synthase (SuSy) was phosphorylated in the elongation zone of maize (Zea mays L.) leaves. The approximately 90-kD subunit of SuSy was 32P-labeled on seryl residue(s) when excised shoots were fed [32P]orthophosphate. Both isoforms of SuSy (the SS1 and SS2 proteins) were phosphorylated in vivo, and tryptic peptide-mapping analysis suggested a single, similar phosphorylation site in both proteins. A combination of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and automated Edman sequencing analysis unequivocally identified the phosphorylation site in the maize SS2 protein as serine-15. This site was phosphorylated in vitro by endogenous protein kinase(s) in a strictly Ca2+-dependent manner. A synthetic peptide, based on the phosphorylation site sequence, was used to identify and partially purify an endogenous Ca2+-dependent protein kinase(s) from the maize leaf elongation zone and expanding spinach leaves. Phosphorylation of SuSy in vitro selectively activates the cleavage reaction by increasing the apparent affinity of the enzyme for sucrose and UDP, suggesting that phosphorylation may be of regulatory significance. Conservation of the phosphorylation site, and the sequences surrounding it, among plant species suggests that phosphorylation of SuSy may be widespread, if not universal, in plants. |
| Databáze: | OpenAIRE |
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