View source for 1ap5


==TYR34->PHE MUTANT OF HUMAN MITOCHONDRIAL MANGANESE SUPEROXIDE DISMUTASE==
<StructureSection load='1ap5' size='340' side='right'caption='[[1ap5]], [[Resolution|resolution]] 2.20&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[1ap5]] is a 2 chain structure with sequence from [https://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1AP5 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1AP5 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]] 2.2&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=MN:MANGANESE+(II)+ION'>MN</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=1ap5 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1ap5 OCA], [https://pdbe.org/1ap5 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=1ap5 RCSB], [https://www.ebi.ac.uk/pdbsum/1ap5 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=1ap5 ProSAT]</span></td></tr>
</table>
== Disease ==
[https://www.uniprot.org/uniprot/SODM_HUMAN SODM_HUMAN] Genetic variation in SOD2 is associated with susceptibility to microvascular complications of diabetes type 6 (MVCD6) [MIM:[https://omim.org/entry/612634 612634]. These are pathological conditions that develop in numerous tissues and organs as a consequence of diabetes mellitus. They include diabetic retinopathy, diabetic nephropathy leading to end-stage renal disease, and diabetic neuropathy. Diabetic retinopathy remains the major cause of new-onset blindness among diabetic adults. It is characterized by vascular permeability and increased tissue ischemia and angiogenesis.
== Function ==
[https://www.uniprot.org/uniprot/SODM_HUMAN SODM_HUMAN] Destroys superoxide anion radicals which are normally produced within the cells and which are toxic to biological systems.<ref>PMID:10334867</ref> 
== Evolutionary Conservation ==
[[Image:Consurf_key_small.gif|200px|right]]
Check<jmol>
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    <scriptWhenChecked>; select protein; define ~consurf_to_do selected; consurf_initial_scene = true; script "/wiki/ConSurf/ap/1ap5_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=1ap5 ConSurf].
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== Publication Abstract from PubMed ==
Tyrosine 34 is a prominent and conserved residue in the active site of the manganese superoxide dismutases in organisms from bacteria to man. We have prepared the mutant containing the replacement Tyr 34 --&gt; Phe (Y34F) in human manganese superoxide dismutase (hMnSOD) and crystallized it in two different crystal forms, orthorhombic and hexagonal. Crystal structures of hMnSOD Y34F have been solved to 1.9 A resolution in a hexagonal crystal form, denoted as Y34Fhex, and to 2.2 A resolution in an orthorhombic crystal form, denoted as Y34Fortho. Both crystal forms give structures that are closely superimposable with that of wild-type hMnSOD, with the phenyl rings of Tyr 34 in the wild type and Phe 34 in the mutant very similar in orientation. Therefore, in Y34F, a hydrogen-bonded relay that links the metal-bound hydroxyl to ordered solvent (Mn-OH to Gln 143 to Tyr 34 to H2O to His 30) is broken. Surprisingly, the loss of the Tyr 34 hydrogen bonds resulted in large increases in stability (measured by Tm), suggesting that the Tyr 34 hydroxyl does not play a role in stabilizing active-site architecture. The functional role of the side chain hydroxyl of Tyr 34 can be evaluated by comparison of the Y34F mutant with the wild-type hMnSOD. Both wild-type and Y34F had kcat/Km near 10(9) M-1 s-1, close to diffusion-controlled; however, Y34F showed kcat for maximal catalysis smaller by 10-fold than the wild type. In addition, the mutant Y34F was more susceptible to product inhibition by peroxide than the wild-type enzyme. This activity profile and the breaking of the hydrogen-bonding chain at the active site caused by the replacement Tyr 34 --&gt; Phe suggest that Tyr 34 is a proton donor for O2* - reduction to H2O2 or is involved indirectly by orienting solvent or other residues for proton transfer. Up to 100 mM buffers in solution failed to enhance catalysis by either Y34F or the wild-type hMnSOD, suggesting that protonation from solution cannot enhance the release of the inhibiting bound peroxide ion, likely reflecting the enclosure of the active site by conserved residues as shown by the X-ray structures. The increased thermostability of the mutant Y34F and equal diffusion-controlled activity of Y34F and wild-type enzymes with normal superoxide levels suggest that evolutionary conservation of active-site residues in metalloenzymes reflects constraints from extreme rather than average cellular conditions. This new hypothesis that extreme rather than normal substrate concentrations are a powerful constraint on residue conservation may apply most strongly to enzyme defenses where the ability to meet extreme conditions directly affects cell survival.

Crystal structure of Y34F mutant human mitochondrial manganese superoxide dismutase and the functional role of tyrosine 34.,Guan Y, Hickey MJ, Borgstahl GE, Hallewell RA, Lepock JR, O'Connor D, Hsieh Y, Nick HS, Silverman DN, Tainer JA Biochemistry. 1998 Apr 7;37(14):4722-30. PMID:9537987<ref>PMID:9537987</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 1ap5" style="background-color:#fffaf0;"></div>

==See Also==
*[[Superoxide dismutase 3D structures|Superoxide dismutase 3D structures]]
== References ==
<references/>
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</StructureSection>
[[Category: Homo sapiens]]
[[Category: Large Structures]]
[[Category: Borgstahl GEO]]
[[Category: Guan Y]]
[[Category: Tainer JA]]