Autogenous modulation of the Bacillus subtilis sacB-levB-yveA levansucrase operon by the levB transcript.
Silencing of levB, the second structural gene of the tricistronic levansucrase operon encoding the endolevanase LevB, decreases the level of levansucrase expression in Bacillus subtilis. Conversely, independent expression of levB greatly stimulates operon expression. This autogenous effect is mediated by the levB transcript, which carries an internal sequence (5'-AAAGCAGGCAA-3') involved in the enhancing effect. In vitro, the levB transcript displays an affinity for the N-terminal fragment of SacY (K(D) 0.2 microM), the regulatory protein that prevents transcription termination of the levansucrase operon. This positive-feedback loop leads to an increase in the operon expression when B. subtilis is growing in the presence of high sucrose concentrations. Under these conditions, extracellular levan synthesized by the fructosyl polymerase activity of levansucrase can be degraded mainly into levanbiose by the action of LevB. Levanbiose is neither taken up nor metabolized by the bacteria. This work modifies the present view of the status of levansucrase in B. subtilis physiology.
Daguer
Jean-Pierre
JP
Institut Jacques Monod, Laboratoire Génétique et Membranes, CNRS - Universités Paris 6 et Paris 7, Tour 43, 2 place Jussieu, 75251 Paris Cedex 05, France.
Geissmann
Thomas
T
Institut Jacques Monod, Laboratoire Génétique et Membranes, CNRS - Universités Paris 6 et Paris 7, Tour 43, 2 place Jussieu, 75251 Paris Cedex 05, France.
Petit-Glatron
Marie-Françoise
MF
Institut Jacques Monod, Laboratoire Génétique et Membranes, CNRS - Universités Paris 6 et Paris 7, Tour 43, 2 place Jussieu, 75251 Paris Cedex 05, France.
Chambert
Régis
R
Institut Jacques Monod, Laboratoire Génétique et Membranes, CNRS - Universités Paris 6 et Paris 7, Tour 43, 2 place Jussieu, 75251 Paris Cedex 05, France.
D026922:Amino Acid Transport Systems, Acidic / Q000096:biosynthesis / Q000235:genetics; D001412:Bacillus subtilis / Q000201:enzymology / Q000235:genetics*; D001426:Bacterial Proteins / Q000378:metabolism; D001483:Base Sequence; D004187:Disaccharides / Q000378:metabolism; D005630:Fructans / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D020868:Gene Silencing; D006026:Glycoside Hydrolases / Q000235:genetics / Q000378:metabolism; D006602:Hexosyltransferases / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009876:Operon; D012329:RNA, Bacterial / Q000032:analysis / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000378:metabolism; D013395:Sucrose / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic
D026922:Amino Acid Transport Systems, Acidic; D001426:Bacterial Proteins; D004187:Disaccharides; D005630:Fructans; D012329:RNA, Bacterial; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; C076894:SacY protein, Bacillus subtilis; D014157:Transcription Factors; C474649:YveA protein, Bacillus subtilis; C077708:levanbiose; D013395:Sucrose; C072599:levan; D006602:Hexosyltransferases; C021513:levansucrase; D006026:Glycoside Hydrolases; C021512:levanase