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

作者：Christopher J. Gisriel, Eduard Elias, Gaozhong Shen, Nathan T. Soulier, David A. Flesher, M. R. Gunner, Gary W. Brudvig, Roberta Croce, Donald A. Bryant · 发表于：Science Advances · 年份：2023 · DOI：10.1126/sciadv.adg0251 · 被引用次数：35 · 研究领域：Photosynthetic Processes and Mechanisms、Biocrusts and Microbial Ecology、Algal biology and biofuel production

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.