View source for 4hrt


==Scapharca tetrameric hemoglobin, unliganded==
<StructureSection load='4hrt' size='340' side='right'caption='[[4hrt]], [[Resolution|resolution]] 1.46&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[4hrt]] is a 8 chain structure with sequence from [https://en.wikipedia.org/wiki/Anadara_inaequivalvis Anadara inaequivalvis]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=4HRT OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=4HRT 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]] 1.46&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=ACE:ACETYL+GROUP'>ACE</scene>, <scene name='pdbligand=HEM:PROTOPORPHYRIN+IX+CONTAINING+FE'>HEM</scene>, <scene name='pdbligand=PO4:PHOSPHATE+ION'>PO4</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=4hrt FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=4hrt OCA], [https://pdbe.org/4hrt PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=4hrt RCSB], [https://www.ebi.ac.uk/pdbsum/4hrt PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=4hrt ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/GLB2A_ANAIN GLB2A_ANAIN] 
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
The clam Scapharca inaequivalvis possesses two cooperative oxygen binding hemoglobins in its red cells: a homodimeric HbI and a heterotetrameric A2B2 HbII. Each AB dimeric half of HbII is assembled in a manner very similar to that of the well-studied HbI. This study presents crystal structures of HbII along with oxygen binding data both in the crystalline state and in wet nanoporous silica gels. Despite very similar ligand-linked structural transitions observed in HbI and HbII crystals, HbII in the crystal or encapsulated in silica gels apparently exhibits minimal cooperativity in oxygen binding, in contrast with the full cooperativity exhibited by HbI crystals. However, oxygen binding curves in the crystal indicate the presence of a significant functional inequivalence of A and B chains. When this inequivalence is taken into account, both crystal and R state gel functional data are consistent with the conservation of a tertiary contribution to cooperative oxygen binding, quantitatively similar to that measured for HbI, and are in keeping with the structural information. Furthermore, our results indicate that to fully express cooperative ligand binding, HbII requires quaternary transitions hampered by crystal lattice and gel encapsulation, revealing greater complexity in cooperative function than the direct communication across a dimeric interface observed in HbI.

Tertiary and Quaternary Allostery in Tetrameric Hemoglobin from Scapharca inaequivalvis.,Ronda L, Bettati S, Henry ER, Kashav T, Sanders JM, Royer WE, Mozzarelli A Biochemistry. 2013 Mar 15. PMID:23458680<ref>PMID:23458680</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 4hrt" style="background-color:#fffaf0;"></div>

==See Also==
*[[Hemoglobin 3D structures|Hemoglobin 3D structures]]
== References ==
<references/>
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</StructureSection>
[[Category: Anadara inaequivalvis]]
[[Category: Large Structures]]
[[Category: Royer WE]]