1zds
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(New page: 200px<br /><applet load="1zds" size="450" color="white" frame="true" align="right" spinBox="true" caption="1zds, resolution 1.55Å" /> '''Crystal Structure of...)
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Revision as of 05:17, 21 November 2007
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Crystal Structure of Met150Gly AfNiR with Acetamide Bound
Overview
In Cu-containing nitrite reductase from Alcaligenes faecalis S-6 the axial, methionine ligand of the type-1 site was replaced (M150G) to make the, copper ion accessible to external ligands that might affect the enzyme's, catalytic activity. The type-1 site optical spectrum of M150G, (A(460)/A(600)=0.71) differs significantly from that of the native nitrite, reductase (A(460)/A(600)=1.3). The midpoint potential of the type-1 site, of nitrite reductase M150G (E(M)=312(+/-5)mV versus hydrogen) is higher, than that of the native enzyme (E(M)=213(+/-5)mV). M150G has a lower, catalytic activity (k(cat)=133(+/-6)s(-1)) than the wild-type nitrite, reductase (k(cat)=416(+/-10)s(-1)). The binding of external ligands to, M150G restores spectral properties, midpoint potential (E(M)<225mV), and, catalytic activity (k(cat)=374(+/-28)s(-1)). Also the M150H, (A(460)/A(600)=7.7, E(M)=104(+/-5)mV, k(cat)=0.099(+/-0.006)s(-1)) and, M150T (A(460)/A(600)=0.085, E(M)=340(+/-5)mV, k(cat)=126(+/-2)s(-1)), variants were characterized. Crystal structures show that the ligands act, as allosteric effectors by displacing Met62, which moves to bind to the Cu, in the position emptied by the M150G mutation. The reconstituted type-1, site has an otherwise unaltered geometry. The observation that removal of, an endogenous ligand can introduce allosteric control in a redox enzyme, suggests potential for structural and functional flexibility of, copper-containing redox sites.
About this Structure
1ZDS is a Single protein structure of sequence from Alcaligenes faecalis with CU and ACM as ligands. Active as Nitrite reductase (NO-forming), with EC number 1.7.2.1 Full crystallographic information is available from OCA.
Reference
A rearranging ligand enables allosteric control of catalytic activity in copper-containing nitrite reductase., Wijma HJ, Macpherson I, Alexandre M, Diederix RE, Canters GW, Murphy ME, Verbeet MP, J Mol Biol. 2006 May 12;358(4):1081-93. Epub 2006 Mar 6. PMID:16574144
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