Journal
BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS
Volume 1857, Issue 9, Pages 1514-1523Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.bbabio.2016.04.285
Keywords
LHCSR3; Chlamydomonas reinhardtii; Light-Harvesting Complex; Redfield model; transient absorption
Categories
Funding
- Netherlands Organization for Scientific Research (NWO), via a FOM (Foundation for Fundamental Research on Matter) program (The thylalcoid membrane: a dynamic switch)
- ERC [281341]
- Russian Foundation for Basic Research [15-04-02136]
- Advanced Investigator ERC [267333]
- NWO-CW via a TOP-grant [700.58.305]
- Netherlands Royal Academy of Sciences (KNAW)
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LHCSR3 is a member of the Light-Harvesting Complexes (LHC) family, which is mainly composed of pigment protein complexes responsible for collecting photons during the first steps of photosynthesis. Unlike related LHCs, EHCSR3 is expressed in stress conditions and has been shown to be essential for the fast component of photoprotection, non-photochemical quenching (NPQ), in the green alga Chlamydomonas reinhardtii. In plants, which do not possess LHCSR homologs, NPQ is triggered by the PSBS protein. Both PSBS and LHCSR3 possess the ability to sense pH changes but, unlike PSBS, LHCSR3 binds multiple pigments. In this work we have analyzed the properties of the pigments bound to LHCSR3 and their excited state dynamics. The data show efficient excitation energy transfer between pigments with rates similar to those observed for the other LHCs. Application of an exciton model based on a template of LHCII, the most abundant LHC, satisfactorily explains the collected steady state and time-resolved spectroscopic data, indicating that LHCSR3 has a LHC-like molecular architecture, although it probably binds less pigments. The model suggests that most of the chlorophylls have similar energy and interactions as in LHCII. The most striking difference is the localization of the lowest energy state, which is not on the Chlorophyll a (Chl a) 610-611-612 triplet as in all the LHCB antennas, but on Chl a613, which is located close to the lumen and to the pH-sensing region of the protein. (C) 2016 Elsevier B.V. All rights reserved.
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