Molecular Anatomy of Plant Photoprotective Switches: The Sensitivity of PsbS to the Environment, Residue by Residue

Nicoletta Liguori*, Sara R.R. Campos, António M. Baptista, Roberta Croce

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

Under strong sunlight, plants avoid photooxidation by quenching the excess absorbed energy. Quenching is triggered by PsbS, a membrane protein that is activated and deactivated by the light-dependent pH changes in the thylakoid lumen. The mechanism of action of this protein is unknown, but it was suggested that several glutamates act as pH sensors. However, the pK a of glutamate is several pH units below the physiological values in the lumen. Thus, how can PsbS sense the pH of the lumen, and how does it respond to it? By applying a nonstandard molecular dynamics method that treats pH explicitly, we show that the lumen-exposed glutamates of PsbS have strongly shifted pK a values and that such shifts are crucial for the pH sensitivity in physiological conditions. We also demonstrate that protonation drives a systematic unfolding of a region key for protein-protein interactions, indicating that PsbS response to pH is a functional conformational switch.

Original languageEnglish
Pages (from-to)1737-1742
Number of pages6
JournalJournal of Physical Chemistry Letters
Volume10
Issue number8
Early online date25 Mar 2019
DOIs
Publication statusPublished - 18 Apr 2019

Keywords

  • PsbS
  • Quenching
  • pKa
  • pH
  • Conformational switch
  • pH-sensing

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