title: Isolation of the patC gene encoding the cystathionine beta-lyase of Lactobacillus delbrueckii subsp. bulgaricus and molecular analysis of inter-strain variability in enzyme biosynthesis.
abstract: The patC gene encoding the cystathionine beta-lyase (CBL) of Lactobacillus delbrueckii subsp. bulgaricus NCDO 1489 was cloned and expressed in Escherichia coli. Overexpression of CBL complemented the methionine auxotrophy of an E. coli metC mutant, demonstrating in vivo that this enzyme functions as a CBL. However, PatC is distinguishable from the MetC CBLs by a low identity in amino acid sequence, a sensitivity to iodoacetic acid, greater thermostability and a lower substrate affinity. Homologues of patC were detected in the 13 Lb. delbrueckii strains studied, but only seven of them showed CBL activity. In constrast to CBL(+) strains, all CBL-deficient strains analysed were auxotrophic for methionine. This supports the hypothesis that CBLs from lactobacilli are probably involved in methionine biosynthesis. Moreover, the results of this study suggest that post-transcriptional mechanisms account for the differences in CBL activities observed between strains of Lb. delbrueckii.
authors.affiliation: Unité de Microbiologie et Génétique, UMR 5122, Université Claude Bernard-Lyon 1, bât. Lwoff, 10 rue Dubois, F-69622 Villeurbanne Cedex, France1.
authors.forename: Dominique
authors.initials: D
authors.lastname: Aubel
authors.affiliation: Nestlé Research Centre, Nestec Ltd, Vers-chez-les-Blancs, CH-1000 Lausanne 26, Switzerland2.
authors.forename: Jacques Edouard
authors.initials: JE
authors.lastname: Germond
authors.affiliation: Unité de Microbiologie et Génétique, UMR 5122, Université Claude Bernard-Lyon 1, bât. Lwoff, 10 rue Dubois, F-69622 Villeurbanne Cedex, France1.
authors.forename: Christophe
authors.initials: C
authors.lastname: Gilbert
authors.affiliation: Unité de Microbiologie et Génétique, UMR 5122, Université Claude Bernard-Lyon 1, bât. Lwoff, 10 rue Dubois, F-69622 Villeurbanne Cedex, France1.
authors.forename: Danièle
authors.initials: D
authors.lastname: Atlan
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification; D003001:Cloning, Molecular; D003470:Culture Media; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D007778:Lactobacillus / Q000145:classification / Q000201:enzymology* / Q000276:immunology; D008190:Lyases / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification; D008715:Methionine / Q000378:metabolism; D008969:Molecular Sequence Data; D017422:Sequence Analysis, DNA
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D008715:Methionine; D008190:Lyases; C019965:cystathionine beta-lyase