title: Cloning and characterization of transcription of the xylAB operon in Thermoanaerobacter ethanolicus.
abstract: The genes encoding xylose isomerase (xylA) and xylulose kinase (xylB) from the thermophilic anaerobe Thermoanaerobacter ethanolicus were found to constitute an operon with the transcription initiation site 169 nucleotides upstream from the previously assigned (K. Dekker, H. Yamagata, K. Sakaguchi, and S. Udaka, Agric. Biol. Chem. 55:221-227, 1991) promoter region. The bicistronic xylAB mRNA was processed by cleavage within the 5'-terminal portion of the XylB-coding sequence. Transcription of xylAB was induced in the presence of xylose, and, unlike in all other xylose-utilizing bacteria studied, was not repressed by glucose. The existence of putative xyl operator sequences suggested that xylose utilization is controlled by a repressor-operator mechanism. The T. ethanolicus xylB gene coded for a 500-amino-acid-residue protein with a deduced amino acid sequence highly homologous to those of other XylBs. This is the first report of an xylB nucleotide sequence and an xyLAB operon from a thermophilic anaerobic bacterium.
authors.affiliation: Department of Animal Sciences, University of Kentucky, Lexington 40546-0215, USA.
authors.forename: M
authors.initials: M
authors.lastname: Erbeznik
authors.forename: K A
authors.initials: KA
authors.lastname: Dawson
authors.forename: H J
authors.initials: HJ
authors.lastname: Strobel
mesh_terms: D019747:Aldose-Ketose Isomerases / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D001421:Bacteria, Anaerobic / Q000201:enzymology / Q000235:genetics*; D001483:Base Sequence; D003001:Cloning, Molecular; D015964:Gene Expression Regulation, Bacterial; D016988:Gram-Positive Asporogenous Rods, Irregular / Q000201:enzymology / Q000235:genetics*; D008969:Molecular Sequence Data; D009875:Operator Regions, Genetic; D009876:Operon; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics* / Q000378:metabolism; D012329:RNA, Bacterial / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012045:Regulatory Sequences, Nucleic Acid; D016415:Sequence Alignment; D014158:Transcription, Genetic; D014994:Xylose / Q000378:metabolism; D014996:Xylulose / Q000378:metabolism
chemical_list: D012329:RNA, Bacterial; D012333:RNA, Messenger; D014996:Xylulose; D014994:Xylose; D017853:Phosphotransferases (Alcohol Group Acceptor); C032700:xylulokinase; D019747:Aldose-Ketose Isomerases; C023298:xylose isomerase