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1r6w

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{{STRUCTURE_1r6w| PDB=1r6w | SCENE= }}
{{STRUCTURE_1r6w| PDB=1r6w | SCENE= }}
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'''Crystal structure of the K133R mutant of o-Succinylbenzoate synthase (OSBS) from Escherichia coli. Complex with SHCHC'''
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===Crystal structure of the K133R mutant of o-Succinylbenzoate synthase (OSBS) from Escherichia coli. Complex with SHCHC===
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==Overview==
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o-Succinylbenzoate synthase (OSBS) from Escherichia coli, a member of the enolase superfamily, catalyzes an exergonic dehydration reaction in the menaquinone biosynthetic pathway in which 2-succinyl-6-hydroxy-2,4-cyclohexadiene-1-carboxylate (SHCHC) is converted to 4-(2'-carboxyphenyl)-4-oxobutyrate (o-succinylbenzoate or OSB). Our previous structural studies of the Mg(2+).OSB complex established that OSBS is a member of the muconate lactonizing enzyme subgroup of the superfamily: the essential Mg(2+) is coordinated to carboxylate ligands at the ends of the third, fourth, and fifth beta-strands of the (beta/alpha)(7)beta-barrel catalytic domain, and the OSB product is located between the Lys 133 at the end of the second beta-strand and the Lys 235 at the end of the sixth beta-strand [Thompson, T. B., Garrett, J. B., Taylor, E. A, Meganathan, R., Gerlt, J. A., and Rayment, I. (2000) Biochemistry 39, 10662-76]. Both Lys 133 and Lys 235 were separately replaced with Ala, Ser, and Arg residues; all six mutants displayed no detectable catalytic activity. The structure of the Mg(2+).SHCHC complex of the K133R mutant has been solved at 1.62 A resolution by molecular replacement starting from the structure of the Mg(2+).OSB complex. This establishes the absolute configuration of SHCHC: the C1-carboxylate and the C6-OH leaving group are in a trans orientation, requiring that the dehydration proceed via a syn stereochemical course. The side chain of Arg 133 is pointed out of the active site so that it cannot function as a general base, whereas in the wild-type enzyme complexed with Mg(2+).OSB, the side chain of Lys 133 is appropriately positioned to function as the only acid/base catalyst in the syn dehydration. The epsilon-ammonium group of Lys 235 forms a cation-pi interaction with the cyclohexadienyl moiety of SHCHC, suggesting that Lys 235 also stabilizes the enediolate anion intermediate in the syn dehydration via a similar interaction.
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{{ABSTRACT_PUBMED_14661953}}
==About this Structure==
==About this Structure==
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[[Category: Enolase superfamily]]
[[Category: Enolase superfamily]]
[[Category: Tim barrel]]
[[Category: Tim barrel]]
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Revision as of 04:25, 28 July 2008

Image:1r6w.png

Template:STRUCTURE 1r6w

Crystal structure of the K133R mutant of o-Succinylbenzoate synthase (OSBS) from Escherichia coli. Complex with SHCHC

Template:ABSTRACT PUBMED 14661953

About this Structure

1R6W is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.

Reference

Evolution of enzymatic activity in the enolase superfamily: structural and mutagenic studies of the mechanism of the reaction catalyzed by o-succinylbenzoate synthase from Escherichia coli., Klenchin VA, Taylor Ringia EA, Gerlt JA, Rayment I, Biochemistry. 2003 Dec 16;42(49):14427-33. PMID:14661953

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