title: Characterization of a loss-of-function mutation in the isopenicillin N synthetase gene of Acremonium chrysogenum.
abstract: The N-2 strain of Acremonium chrysogenum accumulates the beta-lactam precursor tripeptide delta-(L-alpha-amino-adipoyl)-L-cysteinyl-D-valine and has no discernible activity for three of the cephalosporin C (Ce) biosynthetic enzymes. This phenotype is consistent with a mutation either within pcbC [the isopenicillin N synthetase (IPNS)-encoding gene] or in a pathway-regulator gene. To distinguish these possibilities we have cloned and sequenced pcbC from strain N-2. There is a single C----T mutation at nt 854 within the coding sequence, changing aa 285 from proline to leucine. An IPNS-specific monoclonal antibody recognises a catalytically inactive IPNS protein in extracts of N-2 cells. These findings suggest that strain N-2 carries a simple IPNS mutation and that IPNS or its biosynthetic product isopenicillin N is involved in regulation of the later stages of the Ce biosynthetic pathway.
authors.affiliation: Fermentation Development Department, Glaxochem Ltd, Ulverston, Cumbria, U.K.
authors.forename: M
authors.initials: M
authors.lastname: Ramsden
authors.forename: B A
authors.initials: BA
authors.lastname: McQuade
authors.forename: K
authors.initials: K
authors.lastname: Saunders
authors.forename: M K
authors.initials: MK
authors.lastname: Turner
authors.forename: S
authors.initials: S
authors.lastname: Harford
mesh_terms: D000164:Acremonium / Q000201:enzymology / Q000235:genetics*; D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D004798:Enzymes / Q000235:genetics* / Q000378:metabolism; D005285:Fermentation; D005798:Genes, Bacterial; D007700:Kinetics; D008969:Molecular Sequence Data; D009154:Mutation; D010088:Oxidoreductases
chemical_list: D004798:Enzymes; D010088:Oxidoreductases; C038370:isopenicillin N synthetase