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Regulation of expression, genetic organization and substrate specificity of xylose uptake in Bacillus megaterium
Author(s) -
Schmiedel Dagmar,
Kintrup Martin,
Ku¨ster Elke,
Hillen Wolfgang
Publication year - 1997
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.1997.2881654.x
Subject(s) - bacillus megaterium , catabolite repression , xylose , biology , biochemistry , operon , xylose metabolism , terminator (solar) , gene expression , psychological repression , symporter , microbiology and biotechnology , gene , bacteria , genetics , transporter , escherichia coli , ionosphere , physics , astronomy , mutant , fermentation
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 ( K M ) of approx. 100 μM and is competitively inhibited by glucose with an inhibitor constant K I of 16 mM.