title: A photoactive carotenoid protein acting as light intensity sensor.
abstract: Intense sunlight is dangerous for photosynthetic organisms. Cyanobacteria, like plants, protect themselves from light-induced stress by dissipating excess absorbed energy as heat. Recently, it was discovered that a soluble orange carotenoid protein, the OCP, is essential for this photoprotective mechanism. Here we show that the OCP is also a member of the family of photoactive proteins; it is a unique example of a photoactive protein containing a carotenoid as the photoresponsive chromophore. Upon illumination with blue-green light, the OCP undergoes a reversible transformation from its dark stable orange form to a red "active" form. The red form is essential for the induction of the photoprotective mechanism. The illumination induces structural changes affecting both the carotenoid and the protein. Thus, the OCP is a photoactive protein that senses light intensity and triggers photoprotection.
authors.affiliation: Commissariat à l'Energie Atomique, Institut de Biologie et Technologies de Saclay, Centre National de la Recherche Scientifique, 91191 Gif sur Yvette, France.
authors.forename: Adjélé
authors.initials: A
authors.lastname: Wilson
authors.forename: Claire
authors.initials: C
authors.lastname: Punginelli
authors.forename: Andrew
authors.initials: A
authors.lastname: Gall
authors.forename: Cosimo
authors.initials: C
authors.lastname: Bonetti
authors.forename: Maxime
authors.initials: M
authors.lastname: Alexandre
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Routaboul
authors.forename: Cheryl A
authors.initials: CA
authors.lastname: Kerfeld
authors.forename: Rienk
authors.initials: R
authors.lastname: van Grondelle
authors.forename: Bruno
authors.initials: B
authors.lastname: Robert
authors.forename: John T M
authors.initials: JT
authors.lastname: Kennis
authors.forename: Diana
authors.initials: D
authors.lastname: Kirilovsky
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002338:Carotenoids / Q000378:metabolism*; D003116:Color; D008027:Light; D008958:Models, Molecular; D010777:Photochemistry; D017434:Protein Structure, Tertiary; D046939:Synechocystis / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects
chemical_list: D001426:Bacterial Proteins; D002338:Carotenoids