Phycobilisome model with novel skeleton-like structures in a glaucocystophyte Cyanophora paradoxa

Phycobilisome (PBS) is a photosynthetic antenna supercomplex consisting of a central core subcomplex with several peripheral rods radiating from the core. Subunit structure of PBS was studied in a glaucocystophyte Cyanophora paradoxa strain NIES 547. Subunit composition of PBS was identified by N-terminal sequencing and genes for the subunits were determined by homology search of databases. They included rod linker proteins CpcK1 and CpcK2, rod-core linker proteins CpcG1 and CpcG2, and core linker proteins ApcC1 and ApcC2. Subfractionation by native polyacrylamide gel electrophoresis provided evidence for novel subcomplexes (ApcE/CpcK1/CpcG2/ApcA/ApcB/CpcD and ApcE/CpcK2/CpcG1/ApcA/ApcB), which connect rod and core subcomplexes. These skeleton-like structures may serve as a scaffold of the whole PBS assembly. Different roles of ApcC1 and ApcC2 were also suggested. Based on these findings, structural models for PBS were proposed. This article is part of a Special Issue entitled: Photosynthesis Research for Sustainability: from Natural to Artificial.