Structure and quenching of a bundle-shaped phycobilisome.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 41091862.
- Also identified by DOI 10.1126/sciadv.adz6774 and PMC identifier 12525769.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Cyanobacteria use soluble antenna megacomplexes, phycobilisomes (PBSs), to maximize light-harvesting efficiency and small photoswitchable orange carotenoid proteins (OCPs) to down-regulate PBSs in high light. Among known PBS morphologies, the one from the basal cyanobacterial genus <i>Gloeobacter</i> still lacks detailed structural characterization. Here, we reconstructed a cryo-electron microscopy structure of the >10-megadalton <i>Gloeobacter violaceus</i> PBS, with diverging, conformationally mobile bundles of rods composed of stacked phycoerythrin and phycocyanin hexamers, stemming from a pentacylindrical allophycocyanin core belted by auxiliary phycocyanin hexamers. We show how two <i>Gloeobacter</i>-specific multidomain linker proteins, Glr1262 and Glr2806, maintain this bundle-shaped architecture and reveal its differential regulation via nonphotochemical quenching by two OCP types of <i>G. violaceus</i> that recognize separate binding sites within the allophycocyanin core, including lateral cylinders absent in tricylindrical cores.
Medical subject headings
- Phycobilisomes
- Cyanobacteria
- Bacterial Proteins