Catabolite repression of the Bacillus subtilis xyl operon involves a cis element functional in the context of an unrelated sequence, and glucose exerts additional xylR-dependent repression.
Catabolite repression (CR) of xylose utilization by Bacillus subtilis involves a 14-bp cis-acting element (CRE) located in the translated region of the gene encoding xylose isomerase (xylA). Mutations of CRE making it more similar to a previously proposed consensus element lead to increased CR exerted by glucose, fructose, and glycerol. Fusion of CRE to an unrelated, constitutive promoter confers CR to beta-galactosidase expression directed by that promoter. This result demonstrates that CRE can function independently of sequence context and suggests that it is indeed a generally active cis element for CR. In contrast to the other carbon sources studied here, glucose leads to an additional repression of xylA expression, which is independent of CRE and is not found when CRE is fused to the unrelated promoter. This repression requires a functional xylR encoding Xyl repressor and is dependent on the concentrations of glucose and the inducer xylose in the culture broth. Potential mechanisms for this glucose-specific repression are discussed.
Kraus
A
A
Lehrstuhl für Mikrobiologie, Institut für Mikrobiologie, Biochemie und Genetik der Friedrich-Alexander, Universität Erlangen-Nürnberg, Federal Republic of Germany.
Hueck
C
C
Gärtner
D
D
Hillen
W
W
D019747:Aldose-Ketose Isomerases; D001412:Bacillus subtilis / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D002238:Carbohydrate Epimerases / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D005798:Genes, Bacterial / Q000235:genetics / Q000502:physiology*; D005947:Glucose / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics / Q000502:physiology; D009876:Operon / Q000235:genetics / Q000502:physiology*; D012045:Regulatory Sequences, Nucleic Acid / Q000502:physiology*; D014994:Xylose / Q000235:genetics / Q000378:metabolism*
D014994:Xylose; D002238:Carbohydrate Epimerases; D019747:Aldose-Ketose Isomerases; C023298:xylose isomerase; D005947:Glucose