View source for 4un1


==Sirohaem decarboxylase AhbA/B - an enzyme with structural homology to the Lrp/AsnC transcription factor family that is part of the alternative haem biosynthesis pathway.==
<StructureSection load='4un1' size='340' side='right'caption='[[4un1]], [[Resolution|resolution]] 1.97&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[4un1]] is a 4 chain structure with sequence from [https://en.wikipedia.org/wiki/Desulfovibrio_desulfuricans Desulfovibrio desulfuricans]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=4UN1 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=4UN1 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]] 1.97&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=OBV:12,18-DIDECARBOXY-SIROHEME'>OBV</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=4un1 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=4un1 OCA], [https://pdbe.org/4un1 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=4un1 RCSB], [https://www.ebi.ac.uk/pdbsum/4un1 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=4un1 ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/AHBA_DESDA AHBA_DESDA] Involved in siroheme-dependent heme b biosynthesis. Catalyzes the decarboxylation of siroheme into didecarboxysiroheme (PubMed:24865947). Siroheme is decarboxylated to monodecarboxysiroheme, which is in turn decarboxylated to didecarboxysiroheme (PubMed:24865947).<ref>PMID:24865947</ref> 
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
Some bacteria and archaea synthesise haem by an alternative pathway, which involves the sequestration of sirohaem as a metabolic intermediate rather than as a prosthetic group. Along this pathway the two acetic acid side chains attached to C12 and C18 are decarboxylated by sirohaem decarboxylase, a heterodimeric enzyme composed of AhbA and AhbB, to give didecarboxysirohaem. Further modifications catalysed by two related radical SAM enzymes, AhbC and AhbD, transform didecarboxysirohaem into Fe-coproporphyrin III and haem, respectively. The detailed characterisation of sirohaem decarboxylase is reported in molecular detail. Recombinant versions of Desulfovibrio desulfuricans, Desulfovibrio vulgaris and Methanosarcina barkeri AhbA/B have been produced and their physical properties compared. The D. vulgaris and M. barkeri enzyme complexes both copurify with haem, whose redox state influences the activity of the latter. The kinetic parameters of the D. desulfuricans enzyme have been determined, the enzyme crystallised and it structure has been elucidated. The topology of the enzyme reveals that it shares a structural similitude to the AsnC/Lrp family of transcription factors. The active site is formed in the cavity between the two subunits and a AhbA/B-product complex with didecarboxysirohaem has been obtained. A mechanism for the decarboxylation of the kinetically stable carboxyl groups is proposed.

The structure, function and properties of sirohaem decarboxylase - an enzyme with structural homology to a transcription factor family that is part of the alternative haem biosynthesis pathway.,Palmer DJ, Schroeder S, Lawrence AD, Deery E, Lobo SA, Saraiva LM, McLean KJ, Munro AW, Ferguson SJ, Pickersgill RW, Brown DG, Warren MJ Mol Microbiol. 2014 May 28. doi: 10.1111/mmi.12656. PMID:24865947<ref>PMID:24865947</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 4un1" style="background-color:#fffaf0;"></div>
== References ==
<references/>
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</StructureSection>
[[Category: Desulfovibrio desulfuricans]]
[[Category: Large Structures]]
[[Category: Brown DG]]
[[Category: Palmer DJ]]
[[Category: Pickersgill RW]]
[[Category: Warren MJ]]