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Organic & Biomolecular Chemistry

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Paper

Org. Biomol. Chem., 2010, 8, 122 - 127, DOI: 10.1039/b910170e

The crystal structure of an LLL-configured depsipeptide substrate analogue bound to isopenicillin N synthase

Wei Ge, Ian J. Clifton, Jeanette E. Stok, Robert M. Adlington, Jack E. Baldwin and Peter J. Rutledge

Isopenicillin N synthase (IPNS) is a non-heme iron(II) oxidase, which catalyses the biosynthesis of isopenicillin N (IPN) from the tripeptide -L--aminoadipoyl-L-cysteinyl-D-valine (LLD-ACV) in a remarkable oxidative bicyclisation reaction. The natural substrate for IPNS is the LLD-configured tripeptide. LLL-ACV is not turned over by the enzyme, but inhibits turnover of the LLD-tripeptide. The mechanism by which this inhibition takes place is not fully understood. Recent studies have employed a range of LLD-configured depsipeptide substrate analogues in crystallographic studies to probe events preceding -lactam closure in the IPNS reaction cycle. Herein, we report the first crystal structure of IPNS in complex with an LLL-configured depsipeptide analogue, -L--aminoadipoyl-L-cysteine (1-(R)-carboxy-2-thiomethyl)ethyl ester (LLL-ACOmC). This report describes the crystal structure of the IPNS:Fe(II):LLL-ACOmC complex to 2.0 Å resolution, and discusses attempts to oxygenate this complex at high pressure in order to probe the mechanism by which LLL-configured substrates inhibit IPNS catalysis.

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