2muc
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(New page: 200px<br /><applet load="2muc" size="450" color="white" frame="true" align="right" spinBox="true" caption="2muc, resolution 2.30Å" /> '''MUCONATE CYCLOISOMER...)
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Revision as of 10:39, 21 November 2007
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MUCONATE CYCLOISOMERASE VARIANT F329I
Overview
We have refined to 2.3 A resolution two muconate cycloisomerase (MCIase), variant structures, F329I and I54V, that differ from each other and from, wild-type in their activity toward cis,cis-muconate (CCM) and substituted, CCMs. The working and free R-factors for F329I are 17.4/21.6% and for, I54V, 17.6/22.3% with good stereochemistry. Except for the mutated, residue, there are no significant changes in structure. To understand the, differences in enzymatic properties we docked substituted CCMs and CCM, into the active sites of the variants and wild type. The extra space the, mutations create appears to account for most of the enzymatic differences., The lack of other structural changes explains why, although structurally, equivalent changes occur in chloromuconate cycloisomerase (CMCIase), the, changes in themselves do not convert a MCIase into a dehalogenating, CMCIase. Reanalysis of the CMCIase structure revealed only one general, acid/base, K169. The structural implication is that, in 2-chloro-CCM, conversion by CMCIase, the lactone ring of 5-chloromuconolactone rotates, before dehalogenation to bring the acidic C4 proton next to K169., Therefore, K169 alone performs both required protonation and deprotonation, steps, the first at C5 as in MCIase, and the second, after ring rotation, at C4. This distinguishes CMCIase from alpha/beta barrel isomerases and, racemases, which use two different bases.
About this Structure
2MUC is a Single protein structure of sequence from Pseudomonas putida with MN as ligand. Active as Muconate cycloisomerase, with EC number 5.5.1.1 Full crystallographic information is available from OCA.
Reference
Structural basis for the activity of two muconate cycloisomerase variants toward substituted muconates., Schell U, Helin S, Kajander T, Schlomann M, Goldman A, Proteins. 1999 Jan 1;34(1):125-36. PMID:10336378
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