View source for 1ns6

==The 2.1A Structure of Horse (alpha hemichrome/beta met) Hemoglobin at pH 5.4==
<StructureSection load='1ns6' size='340' side='right' caption='[[1ns6]], [[Resolution|resolution]] 2.05&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[1ns6]] is a 2 chain structure with sequence from [http://en.wikipedia.org/wiki/Equus_caballus Equus caballus]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1NS6 OCA]. For a <b>guided tour on the structure components</b> use [http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=1NS6 FirstGlance]. <br>
</td></tr><tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat"><scene name='pdbligand=HEM:PROTOPORPHYRIN+IX+CONTAINING+FE'>HEM</scene></td></tr>
<tr id='related'><td class="sblockLbl"><b>[[Related_structure|Related:]]</b></td><td class="sblockDat">[[1ns9|1ns9]]</td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=1ns6 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1ns6 OCA], [http://www.rcsb.org/pdb/explore.do?structureId=1ns6 RCSB], [http://www.ebi.ac.uk/pdbsum/1ns6 PDBsum]</span></td></tr>
</table>
== Function ==
[[http://www.uniprot.org/uniprot/HBA_HORSE HBA_HORSE]] Involved in oxygen transport from the lung to the various peripheral tissues. [[http://www.uniprot.org/uniprot/HBB_HORSE HBB_HORSE]] Involved in oxygen transport from the lung to the various peripheral tissues. 
== Evolutionary Conservation ==
[[Image:Consurf_key_small.gif|200px|right]]
Check<jmol>
  <jmolCheckbox>
    <scriptWhenChecked>select protein; define ~consurf_to_do selected; consurf_initial_scene = true; script "/wiki/ConSurf/ns/1ns6_consurf.spt"</scriptWhenChecked>
    <scriptWhenUnchecked>script /wiki/extensions/Proteopedia/spt/initialview01.spt</scriptWhenUnchecked>
    <text>to colour the structure by Evolutionary Conservation</text>
  </jmolCheckbox>
</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/chain_selection.php?pdb_ID=2ata ConSurf].
<div style="clear:both"></div>
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
In 1947, Perutz and co-workers reported that crystalline horse methemoglobin undergoes a large lattice transition as the pH is decreased from 7.1 to 5.4. We have determined the pH 7.1 and 5.4 crystal structures of horse methemoglobin at 1.6 and 2.1 A resolution, respectively, and find that this lattice transition involves a 23 A translation of adjacent hemoglobin tetramers as well as changes in alpha heme ligation and the tertiary structure of the alpha subunits. Specifically, when the pH is lowered from 7.1 to 5.4, the Fe(3+) alpha heme groups (but not the beta heme groups) are converted from the aquomet form, in which the proximal histidine [His87(F8)alpha] and a water molecule are the axial heme ligands, to the hemichrome (bishistidine) form, in which the proximal histidine and the distal histidine [His58(E7)alpha] are the axial heme ligands. Hemichrome formation is coupled to a large tertiary structure transition in the eight-residue segment Pro44(CD2)alpha-Gly51(D7)alpha that converts from an extended loop structure at pH 7.1 to a pi-like helix at pH 5.4. The formation of the pi helix forces Phe46(CD4)alpha out of the alpha heme pocket and into the interface between adjacent hemoglobin tetramers where it participates in crystal lattice contacts unique to the pH 5.4 structure. In addition, the transition from aquomet alpha subunits to bishistidine alpha subunits is accompanied by an approximately 1.2 A movement of the alpha heme groups to a more solvent-exposed position as well as the creation of a solvent channel from the interior of the alpha heme pocket to the outside of the tetramer. These changes and the extensive rearrangement of the crystal lattice structure allow the alpha heme group of one tetramer to make direct contact with an alpha heme group on an adjacent tetramer. These results suggest possible functional roles for hemichrome formation in vivo.

A pH-dependent aquomet-to-hemichrome transition in crystalline horse methemoglobin.,Robinson VL, Smith BB, Arnone A Biochemistry. 2003 Sep 2;42(34):10113-25. PMID:12939139<ref>PMID:12939139</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>

==See Also==
*[[Hemoglobin 3D structures|Hemoglobin 3D structures]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Equus caballus]]
[[Category: Arnone, A]]
[[Category: Robinson, V L]]
[[Category: Smith, B B]]
[[Category: Aquomet beta heme]]
[[Category: Bisimidazole alpha heme]]
[[Category: Globin fold]]
[[Category: Hemichrome]]
[[Category: Oxygen storage-transport complex]]