Phycobiliprotein
Encyclopedia
Phycobiliproteins are water-soluble protein
s present in cyanobacteria and certain algae (rhodophytes, cryptomonad
s, glaucocystophytes) that capture light energy, which is then passed on to chlorophyll
s during photosynthesis
. Phycobiliproteins are formed of a complex between proteins and covalently bound phycobilin
s that act as chromophore
s (the light-capturing part). They are most important constituents of the phycobilisome
s.
The major phycobiliproteins are :
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
s present in cyanobacteria and certain algae (rhodophytes, cryptomonad
Cryptomonad
The cryptomonads are a group of algae, most of which have plastids. They are common in freshwater, and also occur in marine and brackish habitats. Each cell is around 10-50 μm in size and flattened in shape, with an anterior groove or pocket...
s, glaucocystophytes) that capture light energy, which is then passed on to chlorophyll
Chlorophyll
Chlorophyll is a green pigment found in almost all plants, algae, and cyanobacteria. Its name is derived from the Greek words χλωρος, chloros and φύλλον, phyllon . Chlorophyll is an extremely important biomolecule, critical in photosynthesis, which allows plants to obtain energy from light...
s during photosynthesis
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...
. Phycobiliproteins are formed of a complex between proteins and covalently bound phycobilin
Phycobilin
Phycobilins are chromophores found in cyanobacteria and in the chloroplasts of red algae, glaucophytes and some cryptomonads...
s that act as chromophore
Chromophore
A chromophore is the part of a molecule responsible for its color. The color arises when a molecule absorbs certain wavelengths of visible light and transmits or reflects others. The chromophore is a region in the molecule where the energy difference between two different molecular orbitals falls...
s (the light-capturing part). They are most important constituents of the phycobilisome
Phycobilisome
Phycobilisomes are light harvesting antennae of photosystem II in cyanobacteria, red algae and glaucophytes.- General structure :Phycobilisomes are protein complexes anchored to thylakoid membranes. They are made of stacks of chromophorylated proteins, the phycobiliproteins, and their associated...
s.
The major phycobiliproteins are :
- PhycoerythrinPhycoerythrinPhycoerythrin is a red protein from the light-harvesting phycobiliprotein family, present in cyanobacteria, red algae and cryptomonads.Like all phycobiliproteins, phycoerythrin is composed of a protein part, organised in a hexameric structure of alpha and beta chains, covalently binding...
- PhycocyaninPhycocyaninPhycocyanin is a pigment from the light-harvesting phycobiliprotein family, along with allophycocyanin and phycoerythrin. It is an accessory pigment to chlorophyll. All phycobiliproteins are water-soluble and therefore cannot exist within the membrane as do carotenoids, but aggregate forming...
- AllophycocyaninAllophycocyaninAllophycocyanin is a protein from the light-harvesting phycobiliprotein family, along with phycocyanin, phycoerythrin and phycoerythrocyanin. It is an accessory pigment to chlorophyll...
- PhycoerythrocyaninPhycoerythrocyaninPhycoerythrocyanin is a kind of phycobiliproteins, magenta chromoprotein involved in photosynthesis of some Cyanobacteria. This chromoprotein consists of alpha- and beta-subunits, generally aggregated as hexamer...