Phycoerythrocyanin is a kind of

phycobiliprotein Phycobiliproteins are water-soluble proteins present in cyanobacteria and certain algae (rhodophytes, cryptomonads, glaucocystophytes). They capture light energy, which is then passed on to chlorophylls during photosynthesis. Phycobiliproteins are ...

, magenta chromoprotein involved in

photosynthesis Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored i ...

of some

Cyanobacteria Cyanobacteria (), also known as Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's common name, blu ...

. This chromoprotein consists of alpha- and beta-subunits, generally aggregated as hexamer. Alpha-phycoerythrocyanin contains a phycoviolobilin, a violet bilin, that covalently attached at Cys-84, and beta-phycoerythrocyanin contains two phycocyanobilins, a blue bilin, that covalently attached at Cys-84 and -155, respectively. Phycoerythrocyanin is similar to

phycocyanin Phycocyanin is a pigment-protein complex from the light-harvesting phycobiliprotein family, along with allophycocyanin and phycoerythrin. It is an accessory pigment to chlorophyll. All phycobiliproteins are water-soluble, so they cannot exist wi ...

, an important component of the light-harvesting complex (

phycobilisome Phycobilisomes are light harvesting antennae of photosystem II in cyanobacteria, red algae and glaucophytes. It was lost in the plastids of green algae / plants (chloroplasts). General structure Phycobilisomes are protein complexes (up to 600 ...

) of cyanobacteria and red algae. While only phycocyanobilin is covalently bound to

, leading to an absorption maximum around 620 nm, phycoerythrocyanin containing both phycoviolobilin and phycocyanobilin leads to an absorption maximum around 575 nm. As both phycoerythrocyanin and phycocyanin have phycocyanobilin acting as the terminal acceptor of energy transfer, they fluoresce around 635 nm, which is absorbed by allophycocyanins that have maximal absorption around 650 nm and maximal fluorescence around 670 nm. Finally, the light energy absorbed by phycoerythrocyanin is transferred to photosynthetic reaction center.

References

Tetrapyrroles {{biochemistry-stub