A photoactive carotenoid protein acting as light intensity sensor.
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.
Wilson
Adjélé
A
Commissariat à l'Energie Atomique, Institut de Biologie et Technologies de Saclay, Centre National de la Recherche Scientifique, 91191 Gif sur Yvette, France.
Punginelli
Claire
C
Gall
Andrew
A
Bonetti
Cosimo
C
Alexandre
Maxime
M
Routaboul
Jean-Marc
JM
Kerfeld
Cheryl A
CA
van Grondelle
Rienk
R
Robert
Bruno
B
Kennis
John T M
JT
Kirilovsky
Diana
D
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
D001426:Bacterial Proteins; D002338:Carotenoids