1r6w
From Proteopedia
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Crystal structure of the K133R mutant of o-Succinylbenzoate synthase (OSBS) from Escherichia coli. Complex with SHCHC
Overview
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.
About this Structure
1R6W is a Single protein structure of sequence from Escherichia coli with MG and 164 as ligands. 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
Page seeded by OCA on Wed Nov 21 01:19:06 2007
