Characterization of a sucrase gene from Staphylococcus xylosus.
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ABSTRACT:
SUBMITTER: Bruckner R
PROVIDER: S-EPMC196229 | biostudies-other | 1993 Feb
REPOSITORIES: biostudies-other
Publications
Characterization of a sucrase gene from Staphylococcus xylosus.
Brückner R R Wagner E E Götz F F
Journal of bacteriology 19930201 3
The Staphylococcus xylosus gene scrB, encoding a sucrase, has been isolated from a genomic library of S. xylosus constructed in Escherichia coli. The gene was detected by its ability to confer utilization of the glucose and fructose residues of raffinose in an E. coli strain that is not able to metabolize galactose. It was found to reside within a 1.8-kb DNA fragment, the nucleotide sequence of which was determined. One large open reading frame, which is preceded by a ribosome binding site, is e ...[more]
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Project description:The lactose utilization genes of Staphylococcus xylosus have been isolated and characterized. The system is comprised of two structural genes, lacP and lacH, encoding the lactose permease and the beta-galactosidase proteins, respectively, and a regulatory gene, lacR, coding for an activator of the AraC/XylS family. The lactose utilization genes are divergently arranged, the lacPH genes being opposite to lacR. The lacPH genes are cotranscribed from one promoter in front of lacP, whereas lacR is transcribed from two promoters of different strengths. Lactose transport as well as beta-galactosidase activity are inducible by the addition of lactose to the growth medium. Primer extension experiments demonstrated that regulation is achieved at the level of lacPH transcription initiation. Inducibility and efficient lacPH transcription are dependent on a functional lacR gene. Inactivation of lacR resulted in low and constitutive lacPH expression. Expression of lacR itself is practically constitutive, since transcription initiated at the major lacR promoter does not respond to the availability of lactose. Only the minor lacR promoter is lactose inducible. Apart from lactose-specific, LacR-dependent control, the lacPH promoter is also subject to carbon catabolite repression mediated by the catabolite control protein CcpA. When glucose is present in the growth medium, lacPH transcription initiation is reduced. Upon ccpA inactivation, repression at the lacPH promoter is relieved. Despite this loss of transcriptional regulation in the ccpA mutant strain, beta-galactosidase activity is still reduced by glucose, suggesting another level of control.
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