View source for 4nd8


==Av Nitrogenase MoFe Protein High pH Form==
<StructureSection load='4nd8' size='340' side='right'caption='[[4nd8]], [[Resolution|resolution]] 2.00&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[4nd8]] is a 4 chain structure with sequence from [http://en.wikipedia.org/wiki/Azotobacter_vinelandii Azotobacter vinelandii]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=4ND8 OCA]. For a <b>guided tour on the structure components</b> use [http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=4ND8 FirstGlance]. <br>
</td></tr><tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat"><scene name='pdbligand=1CL:FE(8)-S(7)+CLUSTER,+OXIDIZED'>1CL</scene>, <scene name='pdbligand=FE:FE+(III)+ION'>FE</scene>, <scene name='pdbligand=HCA:3-HYDROXY-3-CARBOXY-ADIPIC+ACID'>HCA</scene>, <scene name='pdbligand=ICS:IRON-SULFUR-MOLYBDENUM+CLUSTER+WITH+INTERSTITIAL+CARBON'>ICS</scene></td></tr>
<tr id='related'><td class="sblockLbl"><b>[[Related_structure|Related:]]</b></td><td class="sblockDat">[[1m1n|1m1n]]</td></tr>
<tr id='activity'><td class="sblockLbl"><b>Activity:</b></td><td class="sblockDat"><span class='plainlinks'>[http://en.wikipedia.org/wiki/Nitrogenase Nitrogenase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=1.18.6.1 1.18.6.1] </span></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=4nd8 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=4nd8 OCA], [http://pdbe.org/4nd8 PDBe], [http://www.rcsb.org/pdb/explore.do?structureId=4nd8 RCSB], [http://www.ebi.ac.uk/pdbsum/4nd8 PDBsum], [http://prosat.h-its.org/prosat/prosatexe?pdbcode=4nd8 ProSAT]</span></td></tr>
</table>
== Function ==
[[http://www.uniprot.org/uniprot/NIFD_AZOVI NIFD_AZOVI]] This molybdenum-iron protein is part of the nitrogenase complex that catalyzes the key enzymatic reactions in nitrogen fixation. [[http://www.uniprot.org/uniprot/NIFK_AZOVI NIFK_AZOVI]] This molybdenum-iron protein is part of the nitrogenase complex that catalyzes the key enzymatic reactions in nitrogen fixation. 
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
Proton uptake accompanies the reduction of all known substrates by nitrogenase. As a consequence, a higher pH should limit the availability of protons as a substrate essential for turnover, thereby increasing the proportion of more highly reduced forms of the enzyme for further study. The utility of the high-pH approach would appear to be problematic in view of the observation reported by Pham and Burgess [(1993) Biochemistry 32, 13725-13731] that the MoFe-protein undergoes irreversible protein denaturation above pH 8.65. In contrast, we found by both enzyme activity and crystallographic analyses that the MoFe-protein is stable when incubated at pH 9.5. We did observe, however, that at higher pHs and under turnover conditions, the MoFe-protein is slowly inactivated. While a normal, albeit low, level of substrate reduction occurs under these conditions, the MoFe-protein undergoes a complex transformation; initially, the enzyme is reversibly inhibited for substrate reduction at pH 9.5, yet in a second, slower process, the MoFe-protein becomes irreversibly inactivated as measured by substrate reduction activity at the optimal pH of 7.8. The final inactivated MoFe-protein has an increased hydrodynamic radius compared to that of the native MoFe-protein, yet it has a full complement of iron and molybdenum. Significantly, the modified MoFe-protein retains the ability to specifically interact with its nitrogenase partner, the Fe-protein, as judged by the support of ATP hydrolysis and by formation of a tight complex with the Fe-protein in the presence of ATP and aluminum fluoride. The turnover-dependent inactivation coupled to conformational change suggests a mechanism-based transformation that may provide a new probe of nitrogenase catalysis.

Turnover-Dependent Inactivation of the Nitrogenase MoFe-Protein at High pH.,Yang KY, Haynes CA, Spatzal T, Rees DC, Howard JB Biochemistry. 2014 Jan 21;53(2):333-43. doi: 10.1021/bi4014769. Epub 2014 Jan 6. PMID:24392967<ref>PMID:24392967</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 4nd8" style="background-color:#fffaf0;"></div>

==See Also==
*[[Nitrogenase|Nitrogenase]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Azotobacter vinelandii]]
[[Category: Large Structures]]
[[Category: Nitrogenase]]
[[Category: Haynes, C A]]
[[Category: Howard, J B]]
[[Category: Rees, D C]]
[[Category: Spatzal, T]]
[[Category: Yang, K Y]]
[[Category: High ph]]
[[Category: Nifh]]
[[Category: Nitrogen fixation]]
[[Category: Oxidoreductase]]