Allophycocyanin A is a carbon dioxide receptor in the cyanobacterial phycobilisome

• Published in: Nature communications Vol. 13; no. 1; p. 5289
• Main Authors: Guillén-García, Alejandra, Gibson, Savannah E. R., Jordan, Caleb J. C., Ramaswamy, Venkata K., Linthwaite, Victoria L., Bromley, Elizabeth H. C., Brown, Adrian P., Hodgson, David R. W., Blower, Tim R., Verlet, Jan R. R., Degiacomi, Matteo T., Pålsson, Lars-Olof, Cann, Martin J.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 08.09.2022; Nature Publishing Group; Nature Portfolio
• Subjects: 631/326/41/1969; 631/449/1734; 631/45/612; 631/92/458; Binding; Carbon dioxide; Carbon dioxide fixation; Chlorophyll; Chromophores; Cyanobacteria; Energy transfer; Fixation; Fluorescence; Humanities and Social Sciences; Light-harvesting complex; multidisciplinary; Photosynthesis; Photosynthetic apparatus; Photosystem; Science; Science (multidisciplinary); Trimers
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-022-32925-6

Light harvesting is fundamental for production of ATP and reducing equivalents for CO 2 fixation during photosynthesis. However, electronic energy transfer (EET) through a photosystem can harm the photosynthetic apparatus when not balanced with CO 2 . Here, we show that CO 2 binding to the light-harvesting complex modulates EET in photosynthetic cyanobacteria. More specifically, CO 2 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. CO 2 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 CO 2 in the cyanobacterial light-harvesting apparatus and provides insights into photosynthesis regulation. The transfer of electronic energy through a photosystem can harm the photosynthetic apparatus when not balanced with CO 2 fixation. Here, the authors show that CO 2 modulates electronic energy transfer in cyanobacteria by binding to and enhancing the activity of the light-harvesting complex.