Regulation of expression, genetic organization and substrate specificity of xylose uptake in Bacillus megaterium.
Xylose uptake in Bacillus megaterium depends on expression of a putative H+/xylose symporter encoded by xylT, the last gene in the xyl operon. Insertional inactivation of xylT leads to an apparent uptake deficiency determined with whole cells and severely slower growth on xylose as sole carbon source. Expression of xylT is xylose inducible and subject to carbon catabolite repression mediated by CcpA and cre. Northern analysis of the xyl mRNA reveals that a potential stem-loop structure located in the non-translated region between xylA and xylB presumably acts as a transcriptional terminator, as it leads to different amounts of the respective mRNA sections: the 5'-xylA portion is very abundant, while the 3'-xylBT portion constitutes only a fraction of it. XylT has an apparent Michaelis constant (KM) of approx. 100 microM and is competitively inhibited by glucose with an inhibitor constant KI of 16 mM.
Schmiedel
D
D
Lehrstuhl für Mikrobiologie, Institut für Mikrobiologie, Biochemie und Genetik, Friedrich-Alexander Universität Erlangen-Nürnberg, Germany.
Kintrup
M
M
Küster
E
E
Hillen
W
W
D019747:Aldose-Ketose Isomerases; D000595:Amino Acid Sequence; D001410:Bacillus megaterium / Q000235:genetics* / Q000378:metabolism*; D001426:Bacterial Proteins; D001483:Base Sequence; D015152:Blotting, Northern; D002238:Carbohydrate Epimerases / Q000235:genetics*; D050557:Catechol 2,3-Dioxygenase; D004268:DNA-Binding Proteins / Q000235:genetics; D049308:Dioxygenases; D004926:Escherichia coli / Q000235:genetics; D005632:Fructose / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D015971:Gene Expression Regulation, Enzymologic; D005947:Glucose / Q000378:metabolism; D007700:Kinetics; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009876:Operon; D010105:Oxygenases / Q000235:genetics; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics*; D010940:Plant Proteins / Q000235:genetics; D010957:Plasmids; D012329:RNA, Bacterial / Q000032:analysis / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic; D014994:Xylose / Q000378:metabolism
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D010940:Plant Proteins; D012329:RNA, Bacterial; D012333:RNA, Messenger; D012097:Repressor Proteins; C069286:catabolite control proteins, bacteria; C090420:ccr protein, Citrus x paradisi; D005632:Fructose; D014994:Xylose; D010105:Oxygenases; D049308:Dioxygenases; D050557:Catechol 2,3-Dioxygenase; D017853:Phosphotransferases (Alcohol Group Acceptor); C032700:xylulokinase; D002238:Carbohydrate Epimerases; D019747:Aldose-Ketose Isomerases; C023298:xylose isomerase; D005947:Glucose