Journal Article

Protein Phosphorylation in Pea Root Plastids

Katherine Marie Lukaszewski, Caroline Grace Bowsher, Peter John Savory and Michael James Emes

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 42, issue 6, pages 642-649
Published in print June 2001 | ISSN: 0032-0781
Published online June 2001 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pce087
Protein Phosphorylation in Pea Root Plastids

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry

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Protein phosphorylation has been investigated in non-photosynthetic plastids of pea roots. Intact and lysed preparations of plastids were incubated with [γ-32P]ATP and three stromal proteins of sizes 41, 58 and 62 kDa were phosphorylated on a serine residue. No other proteins were significantly labelled under the conditions used. The 62 kDa protein is probably phosphoglucomutase and represents a phosphoenzyme catalytic intermediate. The protein kinase(s) and phosphatase(s) acting on the other proteins were not sensitive to exogenous calcium but were sensitive to magnesium. The protein phosphatase which acts on the 41 kDa protein is possibly of type 2C, whereas that acting on the 58 kDa phosphoprotein did not fall into any class defined by mammalian systems. Metabolism of exogenous glucose 6-phosphate by the oxidative pentose phosphate pathway in intact plastids abolished the phosphorylation of the 58 kDa protein. Dihydroxyacetone phosphate, phosphoenolpyruvate and 3-phosphoglycerate also inhibited phosphorylation of the 58 kDa protein and had a time-dependent effect on the phosphorylation of the 41 kDa protein. The significance of these results in relation to a possible role for protein phosphorylation in these plastids is considered.

Keywords: Key words: Pisum sativum — Plastids — Protein phosphorylation — Roots.; Abbreviations: DHAP, dihydroxyacetone phosphate; Glc1P, glucose 1-phosphate; Glc6P, glucose 6-phosphate; MV, methyl viologen; OPPP, oxidative pentose phosphate pathway; PEP, phosphoenolpyruvic acid; PGA, 3 phosphoglyeric acid; PGM, phosphoglucomutase.

Journal Article.  5286 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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