Allophycocyanin
From Proteopedia
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Blue-green algae such as ''Spirulina'' maximize their light harvesting ability by using phycobiliproteins to absorb light over a broader spectrum. One of these proteins, allophycocyanin, can be seen on the right. It contains a chromophore called <scene name='Allophycocyanin/Pigment/1'>phycocyanobilin</scene>. | Blue-green algae such as ''Spirulina'' maximize their light harvesting ability by using phycobiliproteins to absorb light over a broader spectrum. One of these proteins, allophycocyanin, can be seen on the right. It contains a chromophore called <scene name='Allophycocyanin/Pigment/1'>phycocyanobilin</scene>. | ||
| - | <Structure load='1all' size=' | + | <Structure load='1all' size='350' frame='true' align='right' caption='Allophycocyanin dimer containing phycocyanobilin complex with N-methyl asparagine [[1all]]' scene='Insert optional scene name here' /> |
'''Allophycocyanin''' is a primarily <scene name='Allophycocyanin/2ndary_structure/2'>alpha-helical</scene> protein. It contains <scene name='Allophycocyanin/Subunits/2'>two subunits</scene>, which each have one phycocyanobilin. Allophycocyanin has a complex quaternary structure. First, <scene name='Allophycocyanin/Quaternary_structure/1'>trimers of the dimers</scene> form in a circular fashion, then <scene name='Allophycocyanin/Quaternary_structure_stack/1'>stack</scene> on top of each other to form an antenna-like structure called the phycobilisome. | '''Allophycocyanin''' is a primarily <scene name='Allophycocyanin/2ndary_structure/2'>alpha-helical</scene> protein. It contains <scene name='Allophycocyanin/Subunits/2'>two subunits</scene>, which each have one phycocyanobilin. Allophycocyanin has a complex quaternary structure. First, <scene name='Allophycocyanin/Quaternary_structure/1'>trimers of the dimers</scene> form in a circular fashion, then <scene name='Allophycocyanin/Quaternary_structure_stack/1'>stack</scene> on top of each other to form an antenna-like structure called the phycobilisome. | ||
Revision as of 07:53, 2 December 2015
Blue-green algae such as Spirulina maximize their light harvesting ability by using phycobiliproteins to absorb light over a broader spectrum. One of these proteins, allophycocyanin, can be seen on the right. It contains a chromophore called .
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Allophycocyanin is a primarily protein. It contains , which each have one phycocyanobilin. Allophycocyanin has a complex quaternary structure. First, form in a circular fashion, then on top of each other to form an antenna-like structure called the phycobilisome.
Interestingly, the λmax of the chromophore can be tuned depending upon the protein binding it. For allophycocyanin, the λmax is 650 nm; in another phycobiliprotein, phycocyanin, the λmax is 625 nm, even though it uses the same chromophore. Phycocyanobilin is a highly flexible, linear tetrapyrrole that is covalently attached to the protein by a to a cysteine in the protein. Allophycocyanin holds the in place through a number of intermolecular interactions. forms hydrogen bonds with an amine in the pigment, while interacts with a carboxylic acid that is exposed to the solvent. A key also holds the molecular planar. These interactions stabilize the pigment in the protein and hold the pigment planar. When the protein is unfolded, the pigment is no longer planar, and loses the ability to transfer red light to chlorophyll.
3D Structures of Allophycocyanin
Updated on 02-December-2015
1all – APC – Arthrospira platensis
1b33 – APC – Mastigocladus laminosus
1kn1 – APC – Porphyra yezoensis
2v8a, 4f0u – APC – Thermosynechococcus elongatus
2vjt – APC – Gloeobacter violaceus
3dbj - APC – Thermosynechococcus vulcanus
4po5 – APS α-B subunit + β chain – Synechocystis
