Peridinin
Encyclopedia
Peridinin is a light-harvesting carotenoid
Carotenoid
Carotenoids are tetraterpenoid organic pigments that are naturally occurring in the chloroplasts and chromoplasts of plants and some other photosynthetic organisms like algae, some bacteria, and some types of fungus. Carotenoids can be synthesized fats and other basic organic metabolic building...

, a pigment
Pigment
A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light.Many materials selectively absorb...

 associated with 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...

 and found in the peridinin-chlorophyll-protein (PCP) light-harvesting complex
Light-harvesting complex
A light-harvesting complex is a complex of subunit proteins that may be part of a larger supercomplex of a photosystem, the functional unit in photosynthesis. It is used by plants and photosynthetic bacteria to collect more of the incoming light than would be captured by the photosynthetic reaction...

 in dinoflagellate
Dinoflagellate
The dinoflagellates are a large group of flagellate protists. Most are marine plankton, but they are common in fresh water habitats as well. Their populations are distributed depending on temperature, salinity, or depth...

s, best studied in Amphidinium carterae. The PCP complex is unique in its high ratio of peridinin to chlorophyll; most light-harvesting complexes contain more chlorophyll than carotenoids, but the PCP contains eight peridinin and two chlorophyll molecules arranged to promote peridinin-chlorophyll energy transfer. The PCP complex is a protein
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...

 trimer with an unusual alpha solenoid
Alpha solenoid
An alpha solenoid is a protein fold found in the protein subunits of light-harvesting complexes, particularly in the peridinin chlorophyll proteins of dinoflagellates, and as domains of larger eukaryotic proteins that make up the nuclear pore complex. The fold consists of alpha helices arranged in...

 protein fold
Protein folding
Protein folding is the process by which a protein structure assumes its functional shape or conformation. It is the physical process by which a polypeptide folds into its characteristic and functional three-dimensional structure from random coil....

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