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.
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.
Aubel
Dominique
D
Unité de Microbiologie et Génétique, UMR 5122, Université Claude Bernard-Lyon 1, bât. Lwoff, 10 rue Dubois, F-69622 Villeurbanne Cedex, France1.
Germond
Jacques Edouard
JE
Nestlé Research Centre, Nestec Ltd, Vers-chez-les-Blancs, CH-1000 Lausanne 26, Switzerland2.
Gilbert
Christophe
C
Unité de Microbiologie et Génétique, UMR 5122, Université Claude Bernard-Lyon 1, bât. Lwoff, 10 rue Dubois, F-69622 Villeurbanne Cedex, France1.
Atlan
Danièle
D
Unité de Microbiologie et Génétique, UMR 5122, Université Claude Bernard-Lyon 1, bât. Lwoff, 10 rue Dubois, F-69622 Villeurbanne Cedex, France1.
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
D001426:Bacterial Proteins; D003470:Culture Media; D008715:Methionine; D008190:Lyases; C019965:cystathionine beta-lyase