title: Structural studies on the reaction of isopenicillin N synthase with the substrate analogue delta-(l-alpha-aminoadipoyl)-l-cysteinyl-d-alpha-aminobutyrate.
abstract: Isopenicillin N synthase (IPNS) is a non-haem iron(II) oxidase which catalyses the biosynthesis of isopenicillin N from the tripeptide delta-(L-alpha-aminoadipoyl)-L-cysteinyl-D-valine (ACV). Herein we report crystallographic studies to investigate the reaction of IPNS with the truncated substrate analogue delta-(L-alpha-aminoadipoyl)-L-cysteinyl-D-alpha-aminobutyrate (ACAb). It has been reported previously that this analogue gives rise to three beta-lactam products when incubated with IPNS: two methyl penams and a cepham. Crystal structures of the IPNS-Fe(II)-ACAb and IPNS-Fe(II)-ACAb-NO complexes have now been solved and are reported herein. These structures and modelling studies based on them shed light on the diminished product selectivity shown by IPNS in its reaction with ACAb and further rationalize the presence of certain key residues at the IPNS active site.
authors.affiliation: The Dyson Perrins Laboratory and the Oxford Centre for Molecular Sciences, University of Oxford, South Parks Road, UK.
authors.forename: Alexandra J
authors.initials: AJ
authors.lastname: Long
authors.forename: Ian J
authors.initials: IJ
authors.lastname: Clifton
authors.forename: Peter L
authors.initials: PL
authors.lastname: Roach
authors.forename: Jack E
authors.initials: JE
authors.lastname: Baldwin
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Schofield
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Rutledge
mesh_terms: D001665:Binding Sites; D018360:Crystallography, X-Ray; D005296:Ferrous Compounds / Q000737:chemistry; D008958:Models, Molecular; D008968:Molecular Conformation; D009569:Nitric Oxide / Q000737:chemistry; D009842:Oligopeptides / Q000737:chemistry / Q000378:metabolism*; D010088:Oxidoreductases / Q000737:chemistry / Q000378:metabolism*; D013302:Streptomyces / Q000201:enzymology; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D013816:Thermodynamics
chemical_list: D005296:Ferrous Compounds; D009842:Oligopeptides; C094177:aminoadipoyl-cysteinyl-aminobutyrate; D009569:Nitric Oxide; D010088:Oxidoreductases; C038370:isopenicillin N synthetase