EMD-27382
Helical rods of far-red light-absorbing allophycocyanin in Synechococcus sp.
EMD-27382
Single-particle2.89 Å
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Map released: 05/04/2023
Last modified: 05/04/2023
Sample Organism:
Synechococcus sp. 63AY4M1
Sample: Far-red light allophycocyanin
Fitted models: 8ddy (Avg. Q-score: 0.6)
Deposition Authors: Gisriel CJ
,
Shen GS
,
Soulier NT
,
Flesher DA
,
Brudvig GW
,
Bryant DA
Sample: Far-red light allophycocyanin
Fitted models: 8ddy (Avg. Q-score: 0.6)
Deposition Authors: Gisriel CJ
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Helical allophycocyanin nanotubes absorb far-red light in a thermophilic cyanobacterium.
Gisriel CJ
,
Elias E
,
Shen G
,
Soulier NT
,
Flesher DA
,
Gunner MR
,
Brudvig GW
,
Croce R
,
Bryant DA
(2023) Sci Adv , 9 , eadg0251 - eadg0251
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(2023) Sci Adv , 9 , eadg0251 - eadg0251
Abstract:
To compete in certain low-light environments, some cyanobacteria express a paralog of the light-harvesting phycobiliprotein, allophycocyanin (AP), that strongly absorbs far-red light (FRL). Using cryo-electron microscopy and time-resolved absorption spectroscopy, we reveal the structure-function relationship of this FRL-absorbing AP complex (FRL-AP) that is expressed during acclimation to low light and that likely associates with chlorophyll a-containing photosystem I. FRL-AP assembles as helical nanotubes rather than typical toroids due to alterations of the domain geometry within each subunit. Spectroscopic characterization suggests that FRL-AP nanotubes are somewhat inefficient antenna; however, the enhanced ability to harvest FRL when visible light is severely attenuated represents a beneficial trade-off. The results expand the known diversity of light-harvesting proteins in nature and exemplify how biological plasticity is achieved by balancing resource accessibility with efficiency.
To compete in certain low-light environments, some cyanobacteria express a paralog of the light-harvesting phycobiliprotein, allophycocyanin (AP), that strongly absorbs far-red light (FRL). Using cryo-electron microscopy and time-resolved absorption spectroscopy, we reveal the structure-function relationship of this FRL-absorbing AP complex (FRL-AP) that is expressed during acclimation to low light and that likely associates with chlorophyll a-containing photosystem I. FRL-AP assembles as helical nanotubes rather than typical toroids due to alterations of the domain geometry within each subunit. Spectroscopic characterization suggests that FRL-AP nanotubes are somewhat inefficient antenna; however, the enhanced ability to harvest FRL when visible light is severely attenuated represents a beneficial trade-off. The results expand the known diversity of light-harvesting proteins in nature and exemplify how biological plasticity is achieved by balancing resource accessibility with efficiency.