Helical allophycocyanin nanotubes absorb far-red light in a thermophilic cyanobacterium

Christopher J. Gisriel, Eduard Elias, Gaozhong Shen, Nathan T. Soulier, David A. Flesher, M. R. Gunner, Gary W. Brudvig, Roberta Croce, Donald Ashley Bryant

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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 lightharvesting proteins in nature and exemplify how biological plasticity is achieved by balancing resource accessibility with efficiency.

Original languageEnglish (US)
Article numbereadg0251
JournalScience Advances
Issue number12
StatePublished - Mar 2023

All Science Journal Classification (ASJC) codes

  • General

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