Molecular basis of photoprotection and control of photosynthetic light-harvesting.
In order to maximize their use of light energy in photosynthesis, plants have molecules that act as light-harvesting antennae, which collect light quanta and deliver them to the reaction centres, where energy conversion into a chemical form takes place. The functioning of the antenna responds to the extreme changes in the intensity of sunlight encountered in nature. In shade, light is efficiently harvested in photosynthesis. However, in full sunlight, much of the energy absorbed is not needed and there are vitally important switches to specific antenna states, which safely dissipate the excess energy as heat. This is essential for plant survival, because it provides protection against the potential photo-damage of the photosynthetic membrane. But whereas the features that establish high photosynthetic efficiency have been highlighted, almost nothing is known about the molecular nature of the dissipative states. Recently, the atomic structure of the major plant light-harvesting antenna protein, LHCII, has been determined by X-ray crystallography. Here we demonstrate that this is the structure of a dissipative state of LHCII. We present a spectroscopic analysis of this crystal form, and identify the specific changes in configuration of its pigment population that give LHCII the intrinsic capability to regulate energy flow. This provides a molecular basis for understanding the control of photosynthetic light-harvesting.
Pascal
Andrew A
AA
Service de Biophysique des Fonctions Membranaires, URA2096/CNRS and DBJC/CEA, CEA-Saclay, 91191 Gif-sur-Yvette Cedex, France.
Liu
Zhenfeng
Z
Broess
Koen
K
van Oort
Bart
B
van Amerongen
Herbert
H
Wang
Chao
C
Horton
Peter
P
Robert
Bruno
B
Chang
Wenrui
W
Ruban
Alexander
A
D002734:Chlorophyll / Q000378:metabolism; D003460:Crystallization; D018360:Crystallography, X-Ray; D005453:Fluorescence; D008027:Light; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry / Q000378:metabolism* / Q000528:radiation effects*; D008958:Models, Molecular; D010788:Photosynthesis / Q000502:physiology* / Q000528:radiation effects*; D045332:Photosystem II Protein Complex / Q000737:chemistry / Q000378:metabolism / Q000528:radiation effects; D010860:Pigments, Biological / Q000737:chemistry / Q000378:metabolism; D010944:Plants / Q000737:chemistry / Q000378:metabolism / Q000528:radiation effects; D017434:Protein Structure, Tertiary; D013059:Spectrum Analysis, Raman; D013329:Structure-Activity Relationship
D045342:Light-Harvesting Protein Complexes; D045332:Photosystem II Protein Complex; D010860:Pigments, Biological; D002734:Chlorophyll