phycobilosomes

The Cyanobacteria possess photosynthetic thylakoid membranes studded with phycobilin-containing phycobilosomes (PBSs).

Marine Synechococcus spp. possess one of the most sophisticated antenna complexes found in the Cyanobacteria. It is proposed that, homologous with freshwater Cyanobacteria, PBSs possess six rods radiating around an allophycocyanin core, and that, at low light, rods comprise a single phycocyanin basal hexamer (disk), two phycoerythrin I disks, and three phycoerythrin II disks maintained by linker polypeptides (figure). Two new linkers have been characterized – MpeC and MpeD – that are involved in the binding of phycoerythrin (PE) disks. MpeC binds the middle PEII disk to the proximal disk, and MpeD binds the distal PEI disk to the proximal PEII disk. Phycobiliproteins APC, PC, PEI and PEII are colored pigments that enable these antenna complexes to capture and transfer photons of various energies to the reaction centers.