1qjf: Difference between revisions

Isopenicillin N synthase (IPNS), a non-haem iron-dependent oxidase, catalyses the biosynthesis of isopenicillin N (IPN), the precursor of all, penicillins and cephalosporins. The key steps in this reaction are the two, iron-dioxygen-mediated ring closures of the tripeptide, delta-(L-alpha-aminoadipoyl)-L-cysteinyl-D-valine (ACV). It has been, proposed that the four-membered beta-lactam ring forms initially, associated with a highly oxidized iron(iv)-oxo (ferryl) moiety, which, subsequently mediates closure of the five-membered thiazolidine ring. Here, we describe observation of the IPNS reaction in crystals by X-ray, crystallography. IPNS Fe2+ substrate crystals were grown anaerobically, exposed to high pressures of oxygen to promote reaction and frozen, and, their structures were elucidated by X-ray diffraction. Using the natural, substrate ACV, this resulted in the IPNS x Fe2+ x IPN product complex., With the substrate analogue, delta-(L-alpha-aminoadipoyl)-L-cysteinyl-L-S-methylcysteine (ACmC) in the, crystal, the reaction cycle was interrupted at the monocyclic stage. These, mono- and bicyclic structures support our hypothesis of a two-stage, reaction sequence leading to penicillin. Furthermore, the formation of a, monocyclic sulphoxide product from ACmC is most simply explained by the, interception of a high-valency iron-oxo species.

1QJF is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Emericella_nidulans Emericella nidulans] with SO4, FE2 and ACS as [http://en.wikipedia.org/wiki/ligands ligands]. Structure known Active Site: SA. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1QJF OCA].  

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