View source for 2bq4


==Crystal structure of type I cytochrome c3 from Desulfovibrio africanus==
<StructureSection load='2bq4' size='340' side='right'caption='[[2bq4]], [[Resolution|resolution]] 1.68&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[2bq4]] is a 2 chain structure with sequence from [https://en.wikipedia.org/wiki/Desulfocurvibacter_africanus Desulfocurvibacter africanus]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2BQ4 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=2BQ4 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]] 1.68&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=CA:CALCIUM+ION'>CA</scene>, <scene name='pdbligand=HEC:HEME+C'>HEC</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=2bq4 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=2bq4 OCA], [https://pdbe.org/2bq4 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=2bq4 RCSB], [https://www.ebi.ac.uk/pdbsum/2bq4 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=2bq4 ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/CYC3B_DESAF CYC3B_DESAF] Exchanges electrons with [NiFe] and [Fe] hydrogenases and with the acidic cytochrome c3. Participates in sulfate respiration coupled with phosphorylation by transferring electrons from the enzyme dehydrogenase to ferredoxin.<ref>PMID:8573595</ref> 
== 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/bq/2bq4_consurf.spt"</scriptWhenChecked>
    <scriptWhenUnchecked>script /wiki/extensions/Proteopedia/spt/initialview03.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=2bq4 ConSurf].
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== Publication Abstract from PubMed ==
In Desulfovibrio metabolism, periplasmic hydrogen oxidation is coupled to cytoplasmic sulfate reduction via transmembrane electron transfer complexes. Type II tetraheme cytochrome c3 (TpII-c3), nine-heme cytochrome c (9HcA) and 16-heme cytochrome c (HmcA) are periplasmic proteins associated to these membrane-bound redox complexes and exhibit analogous physiological function. Type I tetraheme cytochrome c3 (TpI-c3) is thought to act as a mediator for electron transfer from hydrogenase to these multihemic cytochromes. In the present work we have investigated Desulfovibrio africanus (Da) and Desulfovibrio vulgaris Hildenborough (DvH) TpI-c3/TpII-c3 complexes. Comparative kinetic experiments of Da TpI-c3 and TpII-c3 using electrochemistry confirm that TpI-c3 is much more efficient than TpII-c3 as an electron acceptor from hydrogenase (second order rate constant k = 9 x 10(8) M(-1) s(-1), K(m) = 0.5 microM as compared to k = 1.7 x 10(7) M(-1) s(-1), K(m) = 40 microM, for TpI-c3 and TpII-c3, respectively). The Da TpI-c3/TpII-c3 complex was characterized at low ionic strength by gel filtration, analytical ultracentrifugation and cross-linking experiments. The thermodynamic parameters were determined by isothermal calorimetry titrations. The formation of the complex is mainly driven by a positive entropy change (deltaS = 137(+/-7) J mol(-1) K(-1) and deltaH = 5.1(+/-1.3) kJ mol(-1)) and the value for the association constant is found to be (2.2(+/-0.5)) x 10(6) M(-1) at pH 5.5. Our thermodynamic results reveal that the net increase in enthalpy and entropy is dominantly produced by proton release in combination with water molecule exclusion. Electrostatic forces play an important role in stabilizing the complex between the two proteins, since no complex formation is detected at high ionic strength. The crystal structure of Da TpI-c3 has been solved at 1.5 angstroms resolution and structural models of the complex have been obtained by NMR and docking experiments. Similar experiments have been carried out on the DvH TpI-c3/TpII-c3 complex. In both complexes, heme IV of TpI-c3 faces heme I of TpII-c3 involving basic residues of TpI-c3 and acidic residues of TpII-c3. A secondary interacting site has been observed in the two complexes, involving heme II of Da TpII-c3 and heme III of DvH TpI-c3 giving rise to a TpI-c3/TpII-c3 molar ratio of 2:1 and 1:2 for Da and DvH complexes, respectively. The physiological significance of these alternative sites in multiheme cytochromes c is discussed.

The type I/type II cytochrome c3 complex: an electron transfer link in the hydrogen-sulfate reduction pathway.,Pieulle L, Morelli X, Gallice P, Lojou E, Barbier P, Czjzek M, Bianco P, Guerlesquin F, Hatchikian EC J Mol Biol. 2005 Nov 18;354(1):73-90. Epub 2005 Sep 29. PMID:16226767<ref>PMID:16226767</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 2bq4" style="background-color:#fffaf0;"></div>

==See Also==
*[[Cytochrome C 3D structures|Cytochrome C 3D structures]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Desulfocurvibacter africanus]]
[[Category: Large Structures]]
[[Category: Czjzek M]]
[[Category: Guerlesquin F]]
[[Category: Hatchikian EC]]
[[Category: Morelli X]]
[[Category: Pieulle L]]