2fen
3-carboxy-cis,cis-muconate lactonizing enzyme from Agrobacterium radiobacter S2
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OverviewOverview
3-carboxy-cis,cis-muconate lactonizing enzymes participate in the, protocatechuate branch of the 3-oxoadipate pathway of various aerobic, bacteria. The gene encoding a 3-carboxy-cis,cis-muconate lactonizing, enzyme (pcaB1S2) was cloned from a gene cluster involved in, protocatechuate degradation by Agrobacterium radiobacter strain S2. This, gene encoded for a 3-carboxy-cis,cis-muconate lactonizing enzyme of 353, amino acids - significantly smaller than all previously studied, 3-carboxy-cis,cis-muconate lactonizing enzymes. This enzyme, ArCMLE1, was, produced in Escherichia coli and shown to convert not only, 3-carboxy-cis,cis-muconate but also 3-sulfomuconate. ArCMLE1 was purified, as a His-tagged enzyme variant, and the basic catalytic constants for the, conversion of 3-carboxy-cis,cis-muconate and 3-sulfomuconate were, determined. In contrast, Agrobacterium tumefaciens, 3-carboxy-cis,cis-muconate lactonizing enzyme 1 could not, despite 87%, sequence identity to ArCMLE1, use 3-sulfomuconate as substrate. The, crystal structure of ArCMLE1 was determined at 2.2 A resolution., Consistent with the sequence, it showed that the C-terminal domain, present in all other members of the fumarase II family, is missing in, ArCMLE1. Nonetheless, both the tertiary and quaternary structures, and the, structure of the active site, are similar to those of Pseudomonas putida, 3-carboxy-cis,cis-muconate lactonizing enzyme. One principal difference is, that ArCMLE1 contains an Arg, as opposed to a Trp, in the active site., This indicates that activation of the carboxylic nucleophile by a, hydrophobic environment is not required for lactonization, unlike earlier, proposals [Yang J, Wang Y, Woolridge EM, Arora V, Petsko GA, Kozarich JW &, Ringe D (2004) Biochemistry43, 10424-10434]. We identified citrate and, isocitrate as noncompetitive inhibitors of ArCMLE1, and found a potential, binding pocket for them on the enzyme outside the active site.
About this StructureAbout this Structure
2FEN is a Single protein structure of sequence from Agrobacterium tumefaciens with and as ligands. Full crystallographic information is available from OCA.
ReferenceReference
Structure and function of the 3-carboxy-cis,cis-muconate lactonizing enzyme from the protocatechuate degradative pathway of Agrobacterium radiobacter S2., Halak S, Lehtio L, Basta T, Burger S, Contzen M, Stolz A, Goldman A, FEBS J. 2006 Nov;273(22):5169-82. Epub 2006 Oct 20. PMID:17054713
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