Allophycocyanin
From Proteopedia
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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. | ||
| - | Allophycocyanin holds the <scene name='Allophycocyanin/Pigment/1'>pigment</scene> in place through a number of intermolecular interactions. | + | 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 <scene name='Allophycocyanin/Cys/1'>thiol linkage</scene> to a cysteine in the protein. Allophycocyanin holds the <scene name='Allophycocyanin/Pigment/1'>pigment</scene> in place through a number of intermolecular interactions. <scene name='Allophycocyanin/Asn73/1'>Asn72</scene> forms hydrogen bonds with an amine in the pigment, while <scene name='Allophycocyanin/Arg86/1'>arginine 86</scene> interacts with a carboxylic acid that is exposed to the solvent. A key <scene name='Allophycocyanin/Asp87/2'>aspartic acid</scene> also holds the molecular planar. These interactions stabilize the pigment in the protein and hold the pigment planar. When the protein is unfolded, the |
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Revision as of 16:59, 4 November 2011
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
