title: Mutations in the listerial proB gene leading to proline overproduction: effects on salt tolerance and murine infection.
abstract: The observed sensitivity of Listeria monocytogenes to the toxic proline analogue L-azetidine-2-carboxylic acid (AZ) suggested that proline synthesis in Listeria may be regulated by feedback inhibition of gamma-glutamyl kinase (GK), the first enzyme of the proline biosynthesis pathway, encoded by the proB gene. Taking advantage of the Epicurian coli mutator strain XL1-Red, we performed random mutagenesis of the recently described proBA operon and generated three independent mutations in the listerial proB homologue, leading to proline overproduction and salt tolerance when expressed in an E. coli (DeltaproBA) background. While each of the mutations (located within a conserved 26-amino-acid region of GK) was shown to confer AZ resistance (AZ(r)) on an L. monocytogenes proBA mutant, listerial transformants failed to exhibit the salt-tolerant phenotype observed in E. coli. Since proline accumulation has previously been linked to the virulence potential of a number of pathogenic bacteria, we analyzed the effect of proline overproduction on Listeria pathogenesis. However, our results suggest that as previously described for proline auxotrophy, proline hyperproduction has no apparent impact on the virulence potential of Listeria.
authors.affiliation: Department of Microbiology and National Food Biotechnology Centre, University College Cork, Cork, Ireland.
authors.forename: R D
authors.initials: RD
authors.lastname: Sleator
authors.forename: C G
authors.initials: CG
authors.lastname: Gahan
authors.forename: C
authors.initials: C
authors.lastname: Hill
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003470:Culture Media; D008089:Listeria monocytogenes / Q000235:genetics / Q000254:growth & development / Q000472:pathogenicity*; D008088:Listeriosis / Q000382:microbiology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D009154:Mutation; D009876:Operon; D017851:Phosphotransferases (Carboxyl Group Acceptor) / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D011392:Proline / Q000096:biosynthesis*; D017422:Sequence Analysis, DNA; D012965:Sodium Chloride / Q000494:pharmacology; D014774:Virulence
chemical_list: D003470:Culture Media; D012965:Sodium Chloride; D011392:Proline; D017851:Phosphotransferases (Carboxyl Group Acceptor); C020650:glutamate 5-kinase