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1ibe

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[[Image:1ibe.jpg|left|200px]]<br /><applet load="1ibe" size="350" color="white" frame="true" align="right" spinBox="true"
 
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caption="1ibe, resolution 1.8&Aring;" />
 
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'''DEOXY-HAEMOGLOBIN TRAPPED IN THE HIGH-AFFINITY (R) STATE'''<br />
 
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==Overview==
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==DEOXY-HAEMOGLOBIN TRAPPED IN THE HIGH-AFFINITY (R) STATE==
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Co-operative oxygen binding by the vertebrate haemoglobins arises from an equilibrium between a quaternary structure with low affinity (T), favoured in the absence of ligand, and a high affinity form (R) adopted by the fully ligated protein. While R state haemoglobin has an oxygen affinity close to that of isolated subunits, the affinity of the T state is roughly 300-fold lower. The mechanism by which the T state restrains ligand binding, and the pathway of the quaternary transition, have been largely revealed by detailed crystallographic analyses of a number of haemoglobin molecules in the equilibrium states, as well as intermediate forms of the T state including partially ligated species. The ligation intermediates of the R state, however, have not been as well characterized structurally. We report here the crystal structure of one such intermediate species, namely, horse deoxyhaemoglobin in the R state, at 1.8 A resolution. While ligand binding in the T state may result in unfavourable stereochemistry in and around the haem-ligand complex, the more plastic R structure appears to accommodate equally well both liganded and ligand-free haem. Loss of ligand at the R state haem results in movements of the haem and shifts of the FG corners, which form characteristic intersubunit contacts that distinguish the quaternary states. The shifts are comparable in magnitude to the corresponding movements associated with de-ligation in the T state, although they differ in direction. These and other differences illustrate how the structural changes in the haem pocket are communicated to the subunit interfaces and how the movements that can occur in the R state may be impeded in the T state.
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<StructureSection load='1ibe' size='340' side='right'caption='[[1ibe]], [[Resolution|resolution]] 1.80&Aring;' scene=''>
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== Structural highlights ==
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<table><tr><td colspan='2'>[[1ibe]] is a 2 chain structure with sequence from [https://en.wikipedia.org/wiki/Equus_caballus Equus caballus]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1IBE OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1IBE FirstGlance]. <br>
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</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 1.8&#8491;</td></tr>
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<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=HEM:PROTOPORPHYRIN+IX+CONTAINING+FE'>HEM</scene></td></tr>
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<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=1ibe FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1ibe OCA], [https://pdbe.org/1ibe PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=1ibe RCSB], [https://www.ebi.ac.uk/pdbsum/1ibe PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=1ibe ProSAT]</span></td></tr>
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</table>
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== Function ==
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[https://www.uniprot.org/uniprot/HBA_HORSE HBA_HORSE] Involved in oxygen transport from the lung to the various peripheral tissues.
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== Evolutionary Conservation ==
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[[Image:Consurf_key_small.gif|200px|right]]
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Check<jmol>
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<jmolCheckbox>
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<scriptWhenChecked>; select protein; define ~consurf_to_do selected; consurf_initial_scene = true; script "/wiki/ConSurf/ib/1ibe_consurf.spt"</scriptWhenChecked>
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<scriptWhenUnchecked>script /wiki/extensions/Proteopedia/spt/initialview01.spt</scriptWhenUnchecked>
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<text>to colour the structure by Evolutionary Conservation</text>
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</jmolCheckbox>
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</jmol>, as determined by [http://consurfdb.tau.ac.il/ ConSurfDB]. You may read the [[Conservation%2C_Evolutionary|explanation]] of the method and the full data available from [http://bental.tau.ac.il/new_ConSurfDB/main_output.php?pdb_ID=1ibe ConSurf].
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<div style="clear:both"></div>
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==About this Structure==
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==See Also==
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1IBE is a [http://en.wikipedia.org/wiki/Protein_complex Protein complex] structure of sequences from [http://en.wikipedia.org/wiki/Equus_caballus Equus caballus] with <scene name='pdbligand=HEM:'>HEM</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1IBE OCA].
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*[[Hemoglobin 3D structures|Hemoglobin 3D structures]]
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__TOC__
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==Reference==
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</StructureSection>
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The crystal structure of horse deoxyhaemoglobin trapped in the high-affinity (R) state., Wilson J, Phillips K, Luisi B, J Mol Biol. 1996 Dec 13;264(4):743-56. PMID:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=8980683 8980683]
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[[Category: Equus caballus]]
[[Category: Equus caballus]]
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[[Category: Protein complex]]
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[[Category: Large Structures]]
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[[Category: Luisi, B.]]
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[[Category: Luisi B]]
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[[Category: Phillips, K.]]
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[[Category: Phillips K]]
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[[Category: Wilson, J.]]
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[[Category: Wilson J]]
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[[Category: HEM]]
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[[Category: erythrocyte]]
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[[Category: heme]]
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[[Category: oxygen transport]]
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[[Category: respiratory protein]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 13:10:06 2008''
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Current revision

DEOXY-HAEMOGLOBIN TRAPPED IN THE HIGH-AFFINITY (R) STATE

PDB ID 1ibe

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