View source for 4aam


==MacA wild-type mixed-valence==
<StructureSection load='4aam' size='340' side='right'caption='[[4aam]], [[Resolution|resolution]] 2.17&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[4aam]] is a 1 chain structure with sequence from [https://en.wikipedia.org/wiki/Geobacter_sulfurreducens_PCA Geobacter sulfurreducens PCA]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=4AAM OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=4AAM 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]] 2.17&#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>, <scene name='pdbligand=SO4:SULFATE+ION'>SO4</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=4aam FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=4aam OCA], [https://pdbe.org/4aam PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=4aam RCSB], [https://www.ebi.ac.uk/pdbsum/4aam PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=4aam ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/Q74FY6_GEOSL Q74FY6_GEOSL] 
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
The metal-reducing delta-proteobacterium Geobacter sulfurreducens produces a large number of c-type cytochromes, many of which have been implicated in the transfer of electrons to insoluble metal oxides. Among these, the dihemic MacA was assigned a central role. Here we have produced G. sulfurreducens MacA by recombinant expression in Escherichia coli and have solved its three-dimensional structure in three different oxidation states. Sequence comparisons group MacA into the family of diheme cytochrome c peroxidases, and the protein indeed showed hydrogen peroxide reductase activity with ABTS(-2) as an electron donor. The observed K(M) was 38.5 +/- 3.7 muM H(2)O(2) and v(max) was 0.78 +/- 0.03 mumol of H(2)O(2).min(-1).mg(-1), resulting in a turnover number k(cat) = 0.46 . s(-1). In contrast, no Fe(III) reductase activity was observed. MacA was found to display electrochemical properties similar to other bacterial diheme peroxidases, in addition to the ability to electrochemically mediate electron transfer to the soluble cytochrome PpcA. Differences in activity between CcpA and MacA can be rationalized with structural variations in one of the three loop regions, loop 2, that undergoes conformational changes during reductive activation of the enzyme. This loop is adjacent to the active site heme and forms an open loop structure rather than a more rigid helix as in CcpA. For the activation of the protein, the loop has to displace the distal ligand to the active site heme, H93, in loop 1. A H93G variant showed an unexpected formation of a helix in loop 2 and disorder in loop 1, while a M297H variant that altered the properties of the electron transfer heme abolished reductive activation.

MacA is a second cytochrome c peroxidase of Geobacter sulfurreducens.,Seidel J, Hoffmann M, Ellis KE, Seidel A, Spatzal T, Gerhardt S, Elliott SJ, Einsle O Biochemistry. 2012 Apr 3;51(13):2747-56. Epub 2012 Mar 23. PMID:22417533<ref>PMID:22417533</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 4aam" style="background-color:#fffaf0;"></div>

==See Also==
*[[Cytochrome c peroxidase 3D structures|Cytochrome c peroxidase 3D structures]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Geobacter sulfurreducens PCA]]
[[Category: Large Structures]]
[[Category: Seidel J]]