Abstract
Light-harvesting complex-II (LHC-II) phosphatase activity has generally been examined in the intact thylakoid membrane. A recent report of peptide-phosphatase activity associated with the chloroplast stromal fraction (Hammer, M.F. et al. (1995) Photosynth Res 44: 107–115) has led to the question of whether this activity is capable of dephosphorylating membrane-bound LHC-II. To this end, heat-treated thylakoid membranes were examined as a potential LHC-II phosphatase substrate. Following incubation of the thylakoid membrane at 60°C for 15 min, the endogenous protein phosphatase and kinase activities were almost eliminated. Heat-inactivated phosphomembranes exhibited minimal dephosphorylation of the light harvesting complex-II. Peptide-phosphatase activities isolated from the thylakoid and stromal fraction were able to dephosphorylate LHC-II in heat-inactivated phosphomembranes. The stromal phosphatase showed highest activity against LHC-II at pH 9. Dephosphorylation of the LHC-II by the stromal enzyme was not inhibited by molybdate, vanadate or tungstate ions, but was partially inhibited by EDTA and a synthetic phosphopeptide mimicking the LHC-II phosphorylation site. Thus, the previously identified stromal phosphatase does appear capable of dephosphorylating authentic LHC-II in vivo.
Similar content being viewed by others
Abbreviations
- CPP:
-
chymotryptic phosphopeptides
- LHC-II:
-
light-harvesting complex of Photosystem II
- MP:
-
protein phosphatase fractionated from the thylakoid membrane
- P2Thr :
-
synthetic phosphopeptide MRK-SAT(p)TKKVW
- SP:
-
protein phosphatase fractionated from the stromal compartment
References
Allen JF (1992) Protein phosphorylation in regulation of photosynthesis. Biochim Biophys Acta 1098: 275–335
Allen JF (1995) Thylakoid protein phosphorylation, state 1-state 2 transitions, and photosystem stoichiometry adjustment: Redox control at multiple levels of gene expression. Physiol Plant 93: 196–205
Arnon DI (1949) Copper enzymes in isolated chloroplasts. Plant Physiol 24: 1–15
Bennett J (1977) Phosphorylation of chloroplast membrane polypeptides. Nature 269: 344–346
Bennett J (1980) Chloroplast phosphoprotein: evidence for a thylakoid-bound phosphoprotein phosphatase. Eur J Biochem 104: 85–89
Bennett J (1991) Protein phosphorylation in green plant chloroplasts. Annu Rev Plant Physiol Plant Mol Biol 42: 281–311
Cheng L, Spangfort MD and Allen JF (1994) Substrate specificity and kinetics of thylakoid phosphoprotein phosphatase reactions. Biochim Biophys Acta 1188: 151–157
Hammer MF, Sarath G, Osterman JC and Markwell J (1995) Assessing modulation of stromal and thylakoid light-harvesting complex-II phosphatase activities with phosphopeptide substrates. Photosynth Res 44: 107–115
Laemmli UK (1970) Cleavage of structural proteins during the assembly of the head of bacteriophage T4. Nature 227: 680–685
MacKintosh C, Coggins J and Cohen P (1991) Plant protein phosphatases: subcellular distribution, detection of protein phosphatase 2C and identification of protein phosphatase 2A as the major quinate dehydrogenase phosphatase. Biochem J 273: 733–738
Markwell JP, Baker NR, Bradbury M and Thornber JP (1984) Use of zinc ions to study thylakoid protein phosphorylation and the state 1-state 2 transitions in vitro. Plant Physiol 74: 348–354
Michel H and Bennett J (1989) Use of synthetic peptides to study the substrate specificity of a thylakoid protein kinase. FEBS Lett 254: 165–170
Shacter E (1984) Organic extraction of Pi with isobutanol/toluene. Anal Biochem 138: 416–420
Silverstein T, Cheng L and Allen JF (1993) Chloroplast thylakoid protein phosphatase reactions are redox-independent and kinetically heterogeneous. FEBS Lett 334: 101–105
Sun G and Markwell J (1992) Lack of types 1 and 2A protein serine(P)/threonine(P) phosphatase activities in chloroplasts. Plant Physiol 100: 620–624
Sun G, Sarath G and Markwell J (1993) Phosphopeptides as substrates for thylakoid protein phosphatase activity. Arch Biochem Biophys 304: 490–495
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Hammer, M.F., Sarath, G. & Markwell, J. Dephosphorylation of the thylakoid membrane light-harvesting complex-II by a stromal protein phosphatase. Photosynth Res 45, 195–201 (1995). https://doi.org/10.1007/BF00015560
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00015560