Catabolite repression of the operon for xylose utilization from Bacillus subtilis W23 is mediated at the level of transcription and depends on a cis site in the xylA reading frame

Abstract

The Bacillus subtilis xyl operon encoding enzymes for xylose utilization is repressed in the absence of xylose and in the presence of glucose. Transcriptional fusions of spoVG-lacZ to this operon show regulation of beta-galactosidase expression by glucose, indicating that glucose repression operates at the level of transcription. A similar result is obtained when glucose is replaced by glycerol, thus defining a general catabolite repression mechanism. A deletion of xylR, which encodes the xylose-sensitive repressor of the operon, does not affect glucose repression. The cis element mediating glucose repression was identified by Bal31 deletion analysis. It is confined to a 34 bp segment located at position +125 downstream of the xyl promoter in the coding sequence for xylose isomerase. Cloning of this segment in the opposite orientation leads to reduced catabolite repression. The homology of this element to various proposed consensus sequences for catabolite repression in B. subtilis is discussed.

Carbon Catabolite Control of the Metabolic Network inBacillus subtilis

“…Besides the cre for amyE, such cre sequences for the gnt, 6,7) xyl, 8,9) and hut 10,11) operons have been identified in the reading frames of gntR, xylA, and hutP respectively, whereas those for the acu and acs operons are in their divergent promoter regions. 12) In ccpA mutants, expression of the gnt, 13,14) xyl, 15) hut, 11) and acu 12) operons, and the acsA gene, 12) is relieved from CCR.…”

Properties and Regulation of the Bifunctional Enzyme HPr Kinase/Phosphatase in Bacillus subtilis

“…This complex has been shown to recognize a cisacting palindromic sequence called cres (catabolite response elements), leading to repression or activation of target gene or operon transcription. There is evidence that CcpA and cre meditate CCR of many catabolic genes or operons such as acsA (acetyl coenzyme A synthetase) (20), xyl (encoding enzymes for xylose utilization) (21,22), gnt (encoding enzymes for gluconate catabolism) (23,24), hut (encoding enzymes involved in histidine catabolism) (25,26), and lev (encoding a fructose-specific PTS and a levanase) (27). CCA involving CcpA as a positively acting regulator has been demonstrated for genes involved in the overflow metabolism for excreting excess glucose, such as ackA encoding acetate kinase (12,28), pta encoding phosphotransacetylase (29), and alsS encoding acetolactate synthase (30).…”

Catabolite repression of the xyl operon in Bacillus megaterium

“…B. megaterium has been used for protein expression (18,26) and as a host with improved stability of plasmids compared with B. subtilis (27,32,34,35 at the level of enzymatic activities (5) was described some time ago, it has only recently been established that catabolite repression for several genes in B. subtilis is mediated at the level of transcription (6, 12). Different cis-acting catabolic control sequences have been proposed for a number of operons (7,15,20,36). Catabolite repression of xyl in B. megaterium is more efficient than that in B. subtilis W23 (8,15,16), thus facilitating the study of effects of other carbon sources repressing less effectively than glucose.…”

“…Different cis-acting catabolic control sequences have been proposed for a number of operons (7,15,20,36). Catabolite repression of xyl in B. megaterium is more efficient than that in B. subtilis W23 (8,15,16), thus facilitating the study of effects of other carbon sources repressing less effectively than glucose. …”