1
|
Gregory A, Hurley B, Tran H, Valentine A, She YM, Knowles V, Plaxton W. In vivo regulatory phosphorylation of the phosphoenolpyruvate carboxylase AtPPC1 in phosphate-starved Arabidopsis thaliana. Biochem J 2009; 420:57-65. [PMID: 19228119 PMCID: PMC2677216 DOI: 10.1042/bj20082397] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2008] [Revised: 02/10/2009] [Accepted: 02/19/2009] [Indexed: 11/17/2022]
Abstract
PEPC [PEP(phosphoenolpyruvate) carboxylase] is a tightly controlled cytosolic enzyme situated at a major branchpoint in plant metabolism. Accumulating evidence indicates important functions for PEPC and PPCK (PEPC kinase) in plant acclimation to nutritional P(i) deprivation. However, little is known about the genetic origin or phosphorylation status of native PEPCs from -P(i) (P(i)-deficient) plants. The transfer of Arabidopsis suspension cells or seedlings to -P(i) growth media resulted in: (i) the marked transcriptional upregulation of genes encoding the PEPC isoenzyme AtPPC1 (Arabidopsis thaliana PEPC1), and PPCK isoenzymes AtPPCK1 and AtPPCK2; (ii) >2-fold increases in PEPC specific activity and in the amount of an immunoreactive 107-kDa PEPC polypeptide (p107); and (iii) In vivo p107 phosphorylation as revealed by immunoblotting of clarified extracts with phosphosite-specific antibodies to Ser-11 (which could be reversed following P(i) resupply). Approx. 1.3 mg of PEPC was purified 660-fold from -P(i) suspension cells to apparent homogeneity with a specific activity of 22.3 units x mg(-1) of protein. Gel filtration, SDS/PAGE and immunoblotting demonstrated that purified PEPC exists as a 440-kDa homotetramer composed of identical p107 subunits. Sequencing of p107 tryptic and Asp-N peptides by tandem MS established that this PEPC is encoded by AtPPC1. P(i)-affinity PAGE coupled with immunoblotting indicated stoichiometric phosphorylation of the p107 subunits of AtPPC1 at its conserved Ser-11 phosphorylation site. Phosphorylation activated AtPPC1 at pH 7.3 by lowering its Km(PEP) and its sensitivity to inhibition by L-malate and L-aspartate, while enhancing activation by glucose 6-phosphate. Our results indicate that the simultaneous induction and In vivo phosphorylation activation of AtPPC1 contribute to the metabolic adaptations of -P(i) Arabidopsis.
Collapse
Key Words
- arabidopsis
- gene expression
- pi starvation
- mass spectrometry
- phosphoenolpyruvate carboxylase kinase (ppck)
- protein phosphorylation
- ab, antibody
- anti-rcpepc igg, anti-(ricinus communis pepc) igg
- atppc1, arabidopsis thaliana pepc1
- cam, crassulacean acid metabolism
- dtt, dithiothreitol
- glc-6-p, glucose 6-phosphate
- maldi, matrix-assisted laser-desorption ionization
- ms medium, murashige and skoog medium
- ms/ms, tandem ms
- p107, 107-kda pepc polypeptide
- omaldi 2, orthogonal maldi 2
- pep, phosphoenolpyruvate
- pepc, pep carboxylase
- +pi, pi-sufficient
- −pi, pi-deficient
- pp2a, protein phosphatase type-2a
- ppck, pepc kinase
- q-tof, quadrupole time-of-flight
- qqtof, quadrupole/quadrupole tof
- rt, reverse transcription
Collapse
Affiliation(s)
- Allison L. Gregory
- *Department of Biochemistry, Queen's University, Kingston, ON, Canada, K7L 3N6
| | - Brenden A. Hurley
- †Department of Biology, Queen's University, Kingston, ON, Canada, K7L 3N6, ‡Plant Metabolomics Group
| | - Hue T. Tran
- †Department of Biology, Queen's University, Kingston, ON, Canada, K7L 3N6, ‡Plant Metabolomics Group
| | - Alexander J. Valentine
- Department of Biotechnology, Faculty of Science, University of the Western Cape, Bellville 7535, South Africa
| | - Yi-Min She
- §Department of Chemistry, Queen's University, Kingston, ON, Canada, K7L 3N6
| | - Vicki L. Knowles
- †Department of Biology, Queen's University, Kingston, ON, Canada, K7L 3N6, ‡Plant Metabolomics Group
| | - William C. Plaxton
- *Department of Biochemistry, Queen's University, Kingston, ON, Canada, K7L 3N6
- †Department of Biology, Queen's University, Kingston, ON, Canada, K7L 3N6, ‡Plant Metabolomics Group
| |
Collapse
|