View source for 1s56


==Crystal Structure of "Truncated" Hemoglobin N (HbN) from Mycobacterium tuberculosis, Soaked with Xe Atoms==
<StructureSection load='1s56' size='340' side='right'caption='[[1s56]], [[Resolution|resolution]] 2.43&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[1s56]] is a 2 chain structure with sequence from [https://en.wikipedia.org/wiki/Mycobacterium_tuberculosis Mycobacterium tuberculosis]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1S56 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1S56 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]] 2.43&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=CYN:CYANIDE+ION'>CYN</scene>, <scene name='pdbligand=HEC:HEME+C'>HEC</scene>, <scene name='pdbligand=HEM:PROTOPORPHYRIN+IX+CONTAINING+FE'>HEM</scene>, <scene name='pdbligand=K:POTASSIUM+ION'>K</scene>, <scene name='pdbligand=PO4:PHOSPHATE+ION'>PO4</scene>, <scene name='pdbligand=XE:XENON'>XE</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=1s56 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1s56 OCA], [https://pdbe.org/1s56 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=1s56 RCSB], [https://www.ebi.ac.uk/pdbsum/1s56 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=1s56 ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/TRHBN_MYCTU TRHBN_MYCTU] Binds oxygen cooperatively with very high affinity (P(50) = 0.013 mmHg at 20 degrees Celsius) because of a fast combination (25 microM(-1).s(-1)) and a slow dissociation (0.2 s(-1)) rate.
== 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/s5/1s56_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/main_output.php?pdb_ID=1s56 ConSurf].
<div style="clear:both"></div>
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
Truncated hemoglobins (trHbs) are small hemoproteins forming a separate cluster within the hemoglobin superfamily; their functional roles in bacteria, plants, and unicellular eukaryotes are marginally understood. Crystallographic investigations have shown that the trHb fold (a two-on-two alpha-helical sandwich related to the globin fold) hosts a protein matrix tunnel system offering a potential path for ligand diffusion to the heme distal site. The tunnel topology is conserved in group I trHbs, although with modulation of its size/structure. Here, we present a crystallographic investigation on trHbs from Mycobacterium tuberculosis, Chlamydomonas eugametos, and Paramecium caudatum, showing that treatment of trHb crystals under xenon pressure leads to binding of xenon atoms at specific (conserved) sites along the protein matrix tunnel. The crystallographic results are in keeping with data from molecular dynamics simulations, where a dioxygen molecule is left free to diffuse within the protein matrix. Modulation of xenon binding over four main sites is related to the structural properties of the tunnel system in the three trHbs and may be connected to their functional roles. In a parallel crystallographic investigation on M. tuberculosis trHbN, we show that butyl isocyanide also binds within the apolar tunnel, in excellent agreement with concepts derived from the xenon binding experiments. These results, together with recent data on atypical CO rebinding kinetics to group I trHbs, underline the potential role of the tunnel system in supporting diffusion, but also accumulation in multiple copies, of low polarity ligands/molecules within group I trHbs.

Heme-ligand tunneling in group I truncated hemoglobins.,Milani M, Pesce A, Ouellet Y, Dewilde S, Friedman J, Ascenzi P, Guertin M, Bolognesi M J Biol Chem. 2004 May 14;279(20):21520-5. Epub 2004 Mar 11. PMID:15016811<ref>PMID:15016811</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
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<div class="pdbe-citations 1s56" style="background-color:#fffaf0;"></div>

==See Also==
*[[Hemoglobin 3D structures|Hemoglobin 3D structures]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Large Structures]]
[[Category: Mycobacterium tuberculosis]]
[[Category: Ascenzi P]]
[[Category: Bolognesi M]]
[[Category: Dewilde S]]
[[Category: Friedman J]]
[[Category: Guertin M]]
[[Category: Milani M]]
[[Category: Ouellet Y]]
[[Category: Pesce A]]