The Reaction Cycle of Isopenicillin N Synthase Observed by X-Ray DiffractionBurzlaff, N.I., Rutledge, P.J., Clifton, I.J., Hensgens, C.M.H., Pickford, M., Adlington, R.M., Roach, P.L., Baldwin, J.E.
(1999) Nature 401: 721
- PubMed: 10537113
- DOI: 10.1038/44400
- Structures With Same Primary Citation
- PubMed Abstract:
- Structure of Isopenicillin N Synthase Complexed with Substrate and the Mechanism of Penicillin Formation
Roach, P.L., Clifton, I.J., Hensgens, C.M., Shibata, N., Schofield, C.J., Hajdu, J., Baldwin, J.E.
(1997) Nature 387: 827
- Crystal Structure of Isopenicillin N Synthase is the First from a New Structural Family of Enzymes
Roach, P.L., Clifton, I.J., Fulop, V., Harlos, K., Barton, G.J., Hajdu, J., Andersson, I., Schofield, C.J., Baldwin, J.E.
(1995) Nature 375: 700
- Crystallization and Preliminary X-Ray Diffraction Studies on Recombinant Isopenicillin N Synthase from Aspergillus Nidulans
Roach, P.L., Schofield, C.J., Baldwin, J.E., Clifton, I.J., Hajdu, J.
(1995) Protein Sci 4: 1007
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 closu ...
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.
The Dyson Perrins Laboratory and the Oxford Centre for Molecular Sciences, University of Oxford, UK.