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Crystal structure of plant light-harvesting complex shows the active, energy-transmitting state.


ABSTRACT: Plants dissipate excess excitation energy as heat by non-photochemical quenching (NPQ). NPQ has been thought to resemble in vitro aggregation quenching of the major antenna complex, light harvesting complex of photosystem II (LHC-II). Both processes are widely believed to involve a conformational change that creates a quenching centre of two neighbouring pigments within the complex. Using recombinant LHC-II lacking the pigments implicated in quenching, we show that they have no particular role. Single crystals of LHC-II emit strong, orientation-dependent fluorescence with an emission maximum at 680 nm. The average lifetime of the main 680 nm crystal emission at 100 K is 1.31 ns, but only 0.39 ns for LHC-II aggregates under identical conditions. The strong emission and comparatively long fluorescence lifetimes of single LHC-II crystals indicate that the complex is unquenched, and that therefore the crystal structure shows the active, energy-transmitting state of LHC-II. We conclude that quenching of excitation energy in the light-harvesting antenna is due to the molecular interaction with external pigments in vitro or other pigment-protein complexes such as PsbS in vivo, and does not require a conformational change within the complex.

SUBMITTER: Barros T 

PROVIDER: S-EPMC2637333 | biostudies-other | 2009 Feb

REPOSITORIES: biostudies-other

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Crystal structure of plant light-harvesting complex shows the active, energy-transmitting state.

Barros Tiago T   Royant Antoine A   Standfuss Jörg J   Dreuw Andreas A   Kühlbrandt Werner W  

The EMBO journal 20090108 3


Plants dissipate excess excitation energy as heat by non-photochemical quenching (NPQ). NPQ has been thought to resemble in vitro aggregation quenching of the major antenna complex, light harvesting complex of photosystem II (LHC-II). Both processes are widely believed to involve a conformational change that creates a quenching centre of two neighbouring pigments within the complex. Using recombinant LHC-II lacking the pigments implicated in quenching, we show that they have no particular role.  ...[more]

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