Phycoerythrin (R-PE), Unconjugated

Phycoethyrin (R-PE) is a 240 kDa protein from the light-harvesting phycobilliprotein family, present in cyanobacteria, red algae and cryptomonads. Like all phycobilliprotein, phycoerythrin is composed of a protein part, organised in a hexameric structure of alpha and beta chains, covalently binding chromophores called phycobilins. In the phycoerythrin family, the phycobilins are: phycoerythrobilin, the typical phycoerythrin acceptor chromophore, and sometimes phycourobilin (marine organisms). Phycoerythrins are the phycobilliprotein which bind the highest number of phycobilins (up to six per alpha-beta subunit dimer).