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==Structure of a far-red induced allophycocyanin from Chroococcidiopsis thermalis sp. PCC 7203== | |||
<StructureSection load='8or7' size='340' side='right'caption='[[8or7]], [[Resolution|resolution]] 2.80Å' scene=''> | |||
== Structural highlights == | |||
<table><tr><td colspan='2'>[[8or7]] is a 4 chain structure with sequence from [https://en.wikipedia.org/wiki/Chroococcidiopsis_thermalis Chroococcidiopsis thermalis]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=8OR7 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=8OR7 FirstGlance]. <br> | |||
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 2.8Å</td></tr> | |||
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=CYC:PHYCOCYANOBILIN'>CYC</scene>, <scene name='pdbligand=K:POTASSIUM+ION'>K</scene>, <scene name='pdbligand=SO4:SULFATE+ION'>SO4</scene></td></tr> | |||
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=8or7 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=8or7 OCA], [https://pdbe.org/8or7 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=8or7 RCSB], [https://www.ebi.ac.uk/pdbsum/8or7 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=8or7 ProSAT]</span></td></tr> | |||
</table> | |||
== Function == | |||
[https://www.uniprot.org/uniprot/K9TVG8_CHRTP K9TVG8_CHRTP] | |||
<div style="background-color:#fffaf0;"> | |||
== Publication Abstract from PubMed == | |||
Far-red absorbing allophycocyanins (APC), identified in cyanobacteria capable of FRL photoacclimation (FaRLiP) and low-light photoacclimation (LoLiP), absorb far-red light, functioning in energy transfer as light-harvesting proteins. We report an optimized method to obtain high purity far-red absorbing allophycocyanin B, AP-B2, of Chroococcidiopsis thermalis sp. PCC7203 by synthesis in Escherichia coli and an improved purification protocol. The crystal structure of the trimer, (PCB-ApcD5/PCB-ApcB2)(3), has been resolved to 2.8 A. The main difference to conventional APCs absorbing in the 650-670 nm range is a largely flat chromophore with the co-planarity extending, in particular, from rings BCD to ring A. This effectively extends the conjugation system of PCB and contributes to the super-red-shifted absorption of the alpha-subunit (lambda(max) = 697 nm). On complexation with the beta-subunit, it is even further red-shifted (lambda(max, absorption) = 707 nm, lambda(max, emission) = 721 nm). The relevance of ring A for this shift is supported by mutagenesis data. A variant of the alpha-subunit, I123M, has been generated that shows an intense FR-band already in the absence of the beta-subunit, a possible model is discussed. Two additional mechanisms are known to red-shift the chromophore spectrum: lactam-lactim tautomerism and deprotonation of the chromophore that both mechanisms appear inconsistent with our data, leaving this question unresolved. | |||
Crystallographic and biochemical analyses of a far-red allophycocyanin to address the mechanism of the super-red-shift.,Zhou LJ, Hoppner A, Wang YQ, Hou JY, Scheer H, Zhao KH Photosynth Res. 2024 Jan 6. doi: 10.1007/s11120-023-01066-2. PMID:38182842<ref>PMID:38182842</ref> | |||
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.<br> | |||
[[Category: | </div> | ||
<div class="pdbe-citations 8or7" style="background-color:#fffaf0;"></div> | |||
== References == | |||
<references/> | |||
__TOC__ | |||
</StructureSection> | |||
[[Category: Chroococcidiopsis thermalis]] | |||
[[Category: Large Structures]] | |||
[[Category: Hoeppner A]] | |||
[[Category: Wang YQ]] | |||
[[Category: Zhao KH]] | |||
[[Category: Zhou LJ]] | |||
Latest revision as of 17:46, 6 November 2024
Structure of a far-red induced allophycocyanin from Chroococcidiopsis thermalis sp. PCC 7203Structure of a far-red induced allophycocyanin from Chroococcidiopsis thermalis sp. PCC 7203
Structural highlights
FunctionPublication Abstract from PubMedFar-red absorbing allophycocyanins (APC), identified in cyanobacteria capable of FRL photoacclimation (FaRLiP) and low-light photoacclimation (LoLiP), absorb far-red light, functioning in energy transfer as light-harvesting proteins. We report an optimized method to obtain high purity far-red absorbing allophycocyanin B, AP-B2, of Chroococcidiopsis thermalis sp. PCC7203 by synthesis in Escherichia coli and an improved purification protocol. The crystal structure of the trimer, (PCB-ApcD5/PCB-ApcB2)(3), has been resolved to 2.8 A. The main difference to conventional APCs absorbing in the 650-670 nm range is a largely flat chromophore with the co-planarity extending, in particular, from rings BCD to ring A. This effectively extends the conjugation system of PCB and contributes to the super-red-shifted absorption of the alpha-subunit (lambda(max) = 697 nm). On complexation with the beta-subunit, it is even further red-shifted (lambda(max, absorption) = 707 nm, lambda(max, emission) = 721 nm). The relevance of ring A for this shift is supported by mutagenesis data. A variant of the alpha-subunit, I123M, has been generated that shows an intense FR-band already in the absence of the beta-subunit, a possible model is discussed. Two additional mechanisms are known to red-shift the chromophore spectrum: lactam-lactim tautomerism and deprotonation of the chromophore that both mechanisms appear inconsistent with our data, leaving this question unresolved. Crystallographic and biochemical analyses of a far-red allophycocyanin to address the mechanism of the super-red-shift.,Zhou LJ, Hoppner A, Wang YQ, Hou JY, Scheer H, Zhao KH Photosynth Res. 2024 Jan 6. doi: 10.1007/s11120-023-01066-2. PMID:38182842[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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