Phycobiliprotein

From Palaeos

"Water soluble fluorescent proteins derived from cyanobacteria and eukaryotic algae. In these organisms, they are used as accessory or antenna pigments for photosynthetic light collection. They absorb energy in portions of the visible spectrum that are poorly utilized by chlorophyll and, through fluorescence energy transfer, convey the energy to chlorophyll at the photosynthetic reaction center. ... The phycobiliproteins are composed of a number of subunits, each having a protein backbone to which linear tetrapyrrole chromophores are covalently bound. All phycobiliproteins contain either phycocyanobilin or phycoerythrobilin chromophores, and may also contain one of three minor bilins; phycourobilin, cryptoviolin [= phycobiliviolin?], or the 697-nm bilin. Each bilin has unique spectral characteristics, which may be further modified by interactions of the subunits and of the chromophore with the apoprotein. The phycobiliproteins in many algae are arranged in subcellular structures called phycobilisomes. These structures allow the pigments to be arranged geometrically in a manner which helps to optimize the capture of light and transfer of energy. All of the phycobiliproteins absorb incident light directly, but in addition they participate in an energy transfer chain within the phycobilisome: phycoerythrin -> phycocyanin -> allophycocyanin -> chlorophyll a." Phycobiliproteins - An Overview.

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