title: Twisting a β-Carotene, an Adaptive Trick from Nature for Dissipating Energy during Photoprotection.
abstract: Cyanobacteria possess a family of one-helix high light-inducible proteins (Hlips) that are homologous to light-harvesting antenna of plants and algae. An Hlip protein, high light-inducible protein D (HliD) purified as a small complex with the Ycf39 protein is evaluated using resonance Raman spectroscopy. We show that the HliD binds two different β-carotenes, each present in two non-equivalent binding pockets with different conformations, having their (0,0) absorption maxima at 489 and 522 nm, respectively. Both populations of β-carotene molecules were in all-trans configuration and the absorption position of the farthest blue-shifted β-carotene was attributed entirely to the polarizability of the environment in its binding pocket. In contrast, the absorption maximum of the red-shifted β-carotene was attributed to two different factors: the polarizability of the environment in its binding pocket and, more importantly, to the conformation of its β-rings. This second β-carotene has highly twisted β-rings adopting a flat conformation, which implies that the effective conjugation length N is extended up to 10.5 modifying the energetic levels. This increase in N will also result in a lower S1energy state, which may provide a permanent energy dissipation channel. Analysis of the carbonyl stretching region for chlorophyll a excitations indicates that the HliD binds six chlorophyll a molecules in five non-equivalent binding sites, with at least one chlorophyll a presenting a slight distortion to its macrocycle. The binding modes and conformations of HliD-bound pigments are discussed with respect to the known structures of LHCII and CP29.
authors.affiliation: From the Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ Paris-Sud, Université Paris-Saclay, F-91198, Gif-sur-Yvette cedex, France, manuel.llansola@cea.fr.
authors.forename: Manuel J
authors.identifier: 0000-0002-8065-9459
authors.initials: MJ
authors.lastname: Llansola-Portoles
authors.affiliation: the Centre Algatech, Institute of Microbiology, Academy of Sciences of the Czech Republic, Třeboň, 379 81, Czech Republic, and.
authors.forename: Roman
authors.initials: R
authors.lastname: Sobotka
authors.affiliation: From the Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ Paris-Sud, Université Paris-Saclay, F-91198, Gif-sur-Yvette cedex, France.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Kish
authors.affiliation: the Centre Algatech, Institute of Microbiology, Academy of Sciences of the Czech Republic, Třeboň, 379 81, Czech Republic, and.
authors.forename: Mahendra Kumar
authors.initials: MK
authors.lastname: Shukla
authors.affiliation: From the Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ Paris-Sud, Université Paris-Saclay, F-91198, Gif-sur-Yvette cedex, France.
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Pascal
authors.affiliation: the Institute of Physics and Biophysics, Faculty of Science, University of South Bohemia, České Budějovice 370 01, Czech Republic.
authors.forename: Tomáš
authors.initials: T
authors.lastname: Polívka
authors.affiliation: From the Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ Paris-Sud, Université Paris-Saclay, F-91198, Gif-sur-Yvette cedex, France.
authors.forename: Bruno
authors.initials: B
authors.lastname: Robert
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry* / Q000235:genetics; D000072417:Protein Domains; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D046939:Synechocystis / Q000737:chemistry* / Q000235:genetics; D019207:beta Carotene / Q000737:chemistry* / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D045342:Light-Harvesting Protein Complexes; D019207:beta Carotene
keywords: carotenoid; chlorophyll; cyanobacteria; light-harvesting complex (antenna complex); photosynthesis