Sites required for GltC-dependent regulation of Bacillus subtilis glutamate synthase expression.
The Bacillus subtilis gltAB genes, coding for the two subunits of glutamate synthase, are transcribed divergently from the gltC gene, encoding a LysR-type transcriptional activator of gltAB. The predicted gltA and gltC transcription start sites are separated by 51 to 52 bp. A 15-bp, consensus binding site (Box I) for LysR-type proteins was found centered at position -64 with respect to the gltA transcription start. This site was shown by mutational analysis to be required both for GltC-mediated activation of gltA and for autorepression of gltC. Box II, which is similar to Box I, is centered 22 bp downstream of Box I and overlaps the -35 region of the gltA promoter. Box II was found to be essential for activation of gltA but not for gltC autoregulation. Introduction of approximately one additional helical turn of DNA between Box I and Box II enhanced gltA expression 7- to 40-fold under nonactivating conditions and about 2-fold under activating conditions. Expression of gltA was dramatically decreased when the distance between Box I and Box II was altered by a nonintegral number of helical turns of DNA. gltC autorepression was abolished by most of the inserts between Box I and Box II but was augmented by adding one helical turn.
Belitsky
B R
BR
Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
Janssen
P J
PJ
Sonenshein
A L
AL
D001412:Bacillus subtilis / Q000201:enzymology / Q000235:genetics*; D001426:Bacterial Proteins; D001483:Base Sequence; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics*; D005798:Genes, Bacterial / Q000235:genetics; D005970:Glutamate Synthase / Q000096:biosynthesis / Q000235:genetics*; D006706:Homeostasis; D008969:Molecular Sequence Data; D009154:Mutation; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D012097:Repressor Proteins / Q000235:genetics / Q000502:physiology*; D017384:Sequence Deletion; D015534:Trans-Activators / Q000235:genetics / Q000502:physiology*; D014158:Transcription, Genetic / Q000235:genetics
D001426:Bacterial Proteins; C095882:GltC protein, Bacillus subtilis; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D015534:Trans-Activators; D005970:Glutamate Synthase