View source for 4wak


==H. influenzae beta-carbonic anhydrase variant W39V/G41A==
<StructureSection load='4wak' size='340' side='right'caption='[[4wak]], [[Resolution|resolution]] 2.49&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[4wak]] is a 2 chain structure with sequence from [https://en.wikipedia.org/wiki/Haemophilus_influenzae_Rd_KW20 Haemophilus influenzae Rd KW20]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=4WAK OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=4WAK 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]] 2.49&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=BCT:BICARBONATE+ION'>BCT</scene>, <scene name='pdbligand=K:POTASSIUM+ION'>K</scene>, <scene name='pdbligand=ZN:ZINC+ION'>ZN</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=4wak FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=4wak OCA], [https://pdbe.org/4wak PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=4wak RCSB], [https://www.ebi.ac.uk/pdbsum/4wak PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=4wak ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/CAN_HAEIN CAN_HAEIN] 
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
Haemophilus influenzae beta-carbonic anhydrase (HICA) has been reverse-engineered in the allosteric site region to resemble the nonallosteric Pisum sativum enzyme in order to identify critical features of allostery and intersusbunit communication. Three variants (W39V/G41A, P48S/A49P, and W39V/G41A/P48S/A49P) were identified, through a comparison with a crystal structure of nonallosteric P. sativum beta-carbonic anhydrase (PSCA, PDB 1EKJ ), to potentially revert HICA to a nonallosteric enzyme. The W39V/G41A and P48S/A49P mutations decreased the apparent kcat/Km proton dependence from 4 to 2 and 1, respectively, increasing the overall maximal kcat/Km to 16 +/- 2 muM-1 s-1 (380% of wild type) and 17 +/- 3 muM-1 s-1 (405% of wild type). The pKa values of the metal-bound water molecule based on the pH-rate profile kinetics (8.32 +/- 0.04 for W39V/G41A and 8.3 +/- 0.1 for P48S/A49P) were also slightly higher than that for the wild-type enzyme (7.74 +/- 0.04). The P48S/A49P variant has lost all pH-rate cooperativity. The W39V/G41A/P48S/A49P variant's kinetics were unusual and were fit with a log-linear function with a slope 0.9 +/- 0.2. The crystal structure of the W39V/G41A variant revealed an active site very similar to the T-state wild-type oligomer with bicarbonate trapped in the escort site. By contrast, the X-ray crystal structure of a proline shift variant (P48S/A49P) reveals that it has adopted an active site conformation nearly identical to that of nonallosteric beta-carbonic anhydrase (R-state) for one chain, including a tight association with the dimer-exchanged N-terminal helices; the second chain in the asymmetric unit is associated in a biologically relevant oligomer, but it adopts a T-state conformation that is not capped by dimer-exchanged N-terminal helices. The hybrid R/T nature of HICA P48S/A49P structurally recapitulates the interruption of pH-rate cooperativity observed for this variant. Comparison of the conformations of the R and T chains of P48S/A49P suggests a new hypothesis to explain HICA allosteric communication that is mediated by the N-terminal helices and anion binding at the dimer interface.

Allosteric Reversion of Haemophilus influenzae beta-Carbonic Anhydrase via a Proline Shift.,Hoffmann KM, Million-Perez HR, Merkhofer R, Nicholson H, Rowlett RS Biochemistry. 2014 Dec 24. PMID:25506786<ref>PMID:25506786</ref>

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

==See Also==
*[[Carbonic anhydrase 3D structures|Carbonic anhydrase 3D structures]]
== References ==
<references/>
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</StructureSection>
[[Category: Haemophilus influenzae Rd KW20]]
[[Category: Large Structures]]
[[Category: Hoffmann KM]]
[[Category: Rowlett RS]]