Phosphopeptides as substrates for thylakoid protein phosphatase activity

Arch Biochem Biophys. 1993 Aug 1;304(2):490-5. doi: 10.1006/abbi.1993.1380.


Lack of a suitable substrate has been a major obstacle in studying the chloroplastic thylakoid membrane protein phosphatase activity. In this study, the suitability of synthetic phosphopeptides for this purpose was investigated. Phosphothreonine-containing phosphopeptides mimicking the N-terminal phosphorylation site of the major thylakoid phosphoprotein, the light-harvesting chlorophyll a/b-binding protein (LHCP-II), were dephosphorylated by isolated peak thylakoid membranes. Phosphopeptides representing unrelated sequences or in which the target phosphothreonine had been changed to a phosphoserine were not dephosphorylated. The dephosphorylation of phosphopeptides by thylakoid membranes was similar to the dephosphorylation of endogenous LHCP-II in its pH-dependence profile, sensitivity to inhibitors, and bivalent cation requirement. The same phosphopeptide analogs of the LHCP-II phosphorylation site inhibited endogenous LHCP-II dephosphorylation in isolated thylakoids, whereas the dephospho-analogs and nonsubstrate phosphopeptides had no effect. Collectively, these results suggest that phosphopeptides mimicking a thylakoid phosphoprotein dephosphorylation site can be exploited for further study of the thylakoid protein phosphatase activity.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Cations, Divalent / pharmacology
  • Cell Compartmentation
  • Chloroplasts / enzymology*
  • Fabaceae / enzymology
  • Hydrogen-Ion Concentration
  • Intracellular Membranes / enzymology*
  • Light-Harvesting Protein Complexes
  • Molecular Sequence Data
  • Phosphopeptides / metabolism*
  • Phosphoprotein Phosphatases / drug effects
  • Phosphoprotein Phosphatases / metabolism*
  • Phosphorylation
  • Photosynthetic Reaction Center Complex Proteins / metabolism*
  • Plants, Medicinal
  • Substrate Specificity


  • Cations, Divalent
  • Light-Harvesting Protein Complexes
  • Phosphopeptides
  • Photosynthetic Reaction Center Complex Proteins
  • Phosphoprotein Phosphatases