View source for 2xv2


==Pseudomonas aeruginosa Azurin with mutated metal-binding loop sequence (CAAHAAM), chemically reduced, pH4.2==
<StructureSection load='2xv2' size='340' side='right'caption='[[2xv2]], [[Resolution|resolution]] 1.60&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[2xv2]] is a 1 chain structure with sequence from [https://en.wikipedia.org/wiki/Pseudomonas_aeruginosa Pseudomonas aeruginosa]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=2XV2 OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=2XV2 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]] 1.6&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=CU1:COPPER+(I)+ION'>CU1</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=2xv2 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=2xv2 OCA], [https://pdbe.org/2xv2 PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=2xv2 RCSB], [https://www.ebi.ac.uk/pdbsum/2xv2 PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=2xv2 ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/AZUR_PSEAE AZUR_PSEAE] Transfers electrons from cytochrome c551 to cytochrome oxidase.
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
The type 1 copper site of a cupredoxin involves coordination by cysteine, histidine, and methionine residues from a single loop. Dissociation and protonation of the histidine ligand on this loop is observed in only certain reduced cupredoxins and can regulate electron-transfer reactivity. This effect is introduced in azurin (AZ) (the wild-type protein has an estimated pK(a) of &lt;2) by mutating the native copper-binding loop (C(112)TFPGH(117)SALM(121), ligands numbered). In this work, we have investigated the influence of loop length alone on histidine ligand protonation by determining the pK(a) value in AZ variants with ligand-containing polyalanine loops of different length. Crystal structures of the Cu(I)-variant with the loop sequence C(112)AAH(115)AAM(118) (AZ2A2A) demonstrate that at pH 4.2 His115 is protonated and no longer coordinated, and the imidazole ring is rotated by 180 degrees . The influence of pH on the reduction potential allows a pK(a) of 5.2 +/- 0.1 for His115 in Cu(I)-AZ2A2A to be determined. In the reduced AZ variants in which the loop sequences C(112)AAAAH(117)AAAM(121) (AZ4A3A) and C(112)AAAAH(117)AAAAM(122) (AZ4A4A) have been introduced, pK(a) values of 4.5 +/- 0.1 and 4.4 +/- 0.1, respectively, are obtained for the His117 ligand. Consistent with these data, the crystal structure of Cu(I)-AZ4A4A at pH 5.3 shows no sign of His117 protonation (crystals were unstable at lower pH values). The loop length range studied matches that which occurs naturally and these investigations indicate that length alone can alter the pK(a) of the coordinating histidine by approximately 1 pH unit. The pK(a) for this histidine ligand varies in native cupredoxins by &gt;5 pH units. Other structural and electronic features, governed primarily by the second-coordination sphere, to which the ligand-binding loop is a major contributor, also alter this important feature. A longer ligand-containing loop made of residues whose side chains are larger and more complex than a methyl group increases the second coordination sphere providing additional scope for tuning the pK(a) of the histidine ligand and other active site properties.

Metal-Binding Loop Length Is a Determinant of the pK(a) of a Histidine Ligand at a Type 1 Copper Site.,Li C, Sato K, Monari S, Salard I, Sola M, Banfield MJ, Dennison C Inorg Chem. 2010 Dec 8. PMID:21141901<ref>PMID:21141901</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 2xv2" style="background-color:#fffaf0;"></div>

==See Also==
*[[Azurin 3D structures|Azurin 3D structures]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Large Structures]]
[[Category: Pseudomonas aeruginosa]]
[[Category: Banfield MJ]]
[[Category: Dennison C]]
[[Category: Li C]]
[[Category: Monari S]]
[[Category: Salard I]]
[[Category: Sato K]]
[[Category: Sola M]]