View source for 5tux


==crystal structure and light induced structural changes in orange carotenoid protein bound with echinenone==
<StructureSection load='5tux' size='340' side='right'caption='[[5tux]], [[Resolution|resolution]] 1.50&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[5tux]] is a 1 chain structure with sequence from [https://en.wikipedia.org/wiki/Synechocystis_sp._PCC_6803_substr._Kazusa Synechocystis sp. PCC 6803 substr. Kazusa]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=5TUX OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=5TUX 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]] 1.5&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=ECH:BETA,BETA-CAROTEN-4-ONE'>ECH</scene>, <scene name='pdbligand=GOL:GLYCEROL'>GOL</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=5tux FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=5tux OCA], [https://pdbe.org/5tux PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=5tux RCSB], [https://www.ebi.ac.uk/pdbsum/5tux PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=5tux ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/OCP_SYNY3 OCP_SYNY3] Acts as a photo-protectant. Essential for inhibiting white and blue-green light non-photochemical quenching (NPQ). Binding carotenoids improves OCP's intrinsic photoprotectant activity by broadening its absorption spectrum and facilitating the dissipation of absorbed energy.<ref>PMID:16531492</ref> 
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
Photoprotection is essential for efficient photosynthesis. Cyanobacteria have evolved a unique photoprotective mechanism mediated by a water-soluble carotenoid-based photoreceptor known as orange carotenoid protein (OCP). OCP undergoes large conformational changes in response to intense blue light, and the photoactivated OCP facilitates dissipation of excess energy via direct interaction with allophycocyanins at the phycobilisome core. However, the structural events leading up to the OCP photoactivation remain elusive at the molecular level. Here we present direct observations of light-induced structural changes in OCP captured by dynamic crystallography. Difference electron densities between the dark and illuminated states reveal widespread and concerted atomic motions that lead to altered protein-pigment interactions, displacement of secondary structures, and domain separation. Based on these crystallographic observations together with site-directed mutagenesis, we propose a molecular mechanism for OCP light perception, in which the photochemical property of a conjugated carbonyl group is exploited. We hypothesize that the OCP photoactivation starts with keto-enol tautomerization of the essential 4-keto group in the carotenoid, which disrupts the strong hydrogen bonds between the bent chromophore and the protein moiety. Subsequent structural changes trapped in the crystal lattice offer a high-resolution glimpse of the initial molecular events as OCP begins to transition from the orange-absorbing state to the active red-absorbing state.

Photoactivation mechanism of a carotenoid-based photoreceptor.,Bandara S, Ren Z, Lu L, Zeng X, Shin H, Zhao KH, Yang X Proc Natl Acad Sci U S A. 2017 Jun 13;114(24):6286-6291. doi:, 10.1073/pnas.1700956114. Epub 2017 May 30. PMID:28559328<ref>PMID:28559328</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 5tux" style="background-color:#fffaf0;"></div>
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Large Structures]]
[[Category: Synechocystis sp. PCC 6803 substr. Kazusa]]
[[Category: Bandara S]]
[[Category: Ren Z]]
[[Category: Yang X]]