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Allophycocyanin A is a carbon dioxide receptor in the cyanobacterial phycobilisome

Guillen-Garcia, A. and Gibson, S. and Jordan, C. and Ramaswamy, V. and Linthwaite, V. and Bromley, E.H.C. and Brown, A.P. and Hodgson, D. and Blower, T. and Verlet, J. and Degiacomi, M. and Palsson, L-O. and Cann, M.J. (2022) 'Allophycocyanin A is a carbon dioxide receptor in the cyanobacterial phycobilisome.', Nature Communications, 13 . p. 5289.


Light harvesting is fundamental for production of ATP and reducing equivalents for CO2 fixation during photosynthesis. However, electronic energy transfer (EET) through a photosystem can harm the photosynthetic apparatus when not balanced with CO2. Here, we show that CO2 binding to the light-harvesting complex modulates EET in photosynthetic cyanobacteria. More specifically, CO2 binding to the allophycocyanin alpha subunit of the light-harvesting complex regulates EET and its fluorescence quantum yield in the cyanobacterium Synechocystis sp. PCC 6803. CO2 binding decreases the inter-chromophore distance in the allophycocyanin trimer. The result is enhanced EET in vitro and in live cells. Our work identifies a direct target for CO2 in the cyanobacterial light-harvesting apparatus and provides insights into photosynthesis regulation.

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Publisher statement:This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit
Date accepted:24 August 2022
Date deposited:09 September 2022
Date of first online publication:08 September 2022
Date first made open access:09 September 2022

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