title: Regulation of light harvesting in the green alga Chlamydomonas reinhardtii: the C-terminus of LHCSR is the knob of a dimmer switch.
abstract: Feedback mechanisms that dissipate excess photoexcitations in light-harvesting complexes (LHCs) are necessary to avoid detrimental oxidative stress in most photosynthetic eukaryotes. Here we demonstrate the unique ability of LHCSR, a stress-related LHC from the model organism Chlamydomonas reinhardtii, to sense pH variations, reversibly tuning its conformation from a light-harvesting state to a dissipative one. This conformational change is induced exclusively by the acidification of the environment, and the magnitude of quenching is correlated to the degree of acidification of the environment. We show that this ability to respond to different pH values is missing in the related major LHCII, despite high structural homology. Via mutagenesis and spectroscopic characterization, we show that LHCSR's uniqueness relies on its peculiar C-terminus subdomain, which acts as a sensor of the lumenal pH, able to tune the quenching level of the complex.
authors.affiliation: Department of Physics and Astronomy and Institute for Lasers, Life and Biophotonics, Faculty of Sciences, VU University Amsterdam , De Boelelaan 1081, 1081 HV, Amsterdam, The Netherlands.
authors.forename: Nicoletta
authors.initials: N
authors.lastname: Liguori
authors.forename: Laura M
authors.initials: LM
authors.lastname: Roy
authors.forename: Milena
authors.initials: M
authors.lastname: Opacic
authors.forename: Grégory
authors.initials: G
authors.lastname: Durand
authors.forename: Roberta
authors.initials: R
authors.lastname: Croce
mesh_terms: D016825:Chlamydomonas reinhardtii / Q000378:metabolism*; D045342:Light-Harvesting Protein Complexes / Q000378:metabolism*
chemical_list: D045342:Light-Harvesting Protein Complexes