Allophycocyanin
From Proteopedia
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| + | <StructureSection load='1all' size='400' side='right' scene='' caption='Allophycocyanin dimer containing phycocyanobilin complex with N-methyl asparagine [[1all]]'> | ||
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>. | ||
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| - | <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. | ||
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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 pigment is no longer planar, and loses the ability to transfer red light to chlorophyll.<ref>PMID:23201474</ref> For the most part, <scene name='47/471747/Hydrophobic/1'>hydrophobic</scene> residues (shown in grey) tend to be buried in the middle of the protein or along interaction surfaces. | 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 pigment is no longer planar, and loses the ability to transfer red light to chlorophyll.<ref>PMID:23201474</ref> For the most part, <scene name='47/471747/Hydrophobic/1'>hydrophobic</scene> residues (shown in grey) tend to be buried in the middle of the protein or along interaction surfaces. | ||
| - | + | </StructureSection> | |
== 3D Structures of Allophycocyanin == | == 3D Structures of Allophycocyanin == | ||
Revision as of 11:39, 2 May 2018
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3D Structures of Allophycocyanin
Updated on 02-May-2018
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
3jbb – APS α-B subunit + β chain – Halomicronema Hongdechloris
4rmp – APS – Phormidium
5tjf – APS α + β subunit – Gracilaria chilensis
References
- ↑ Marx A, Adir N. Allophycocyanin and phycocyanin crystal structures reveal facets of phycobilisome assembly. Biochim Biophys Acta. 2013 Mar;1827(3):311-8. doi: 10.1016/j.bbabio.2012.11.006. , Epub 2012 Nov 28. PMID:23201474 doi:http://dx.doi.org/10.1016/j.bbabio.2012.11.006
