Expression of a novel gene, gluP, is essential for normal Bacillus subtilis cell division and contributes to glucose export.
BACKGROUND
The Bacillus subtilis glucokinase operon was predicted to be comprised of the genes, yqgP (now named gluP), yqgQ, and glcK. We have previously established a role for glcK in glucose metabolism. In the absence of enzymes that phosphorylate glucose, such as GlcK and/or enzyme IIGlc, accumulated cytoplasmic glucose can be transported out of the cell. Genes within the glucokinase operon were not previously known to play a role in glucose transport. Here we describe the expression of gluP and its function in glucose transport.


RESULTS
We found that transcription of the glucokinase operon was regulated, putatively, by two promoters: sigmaA and sigmaH. Putative sigmaA and sigmaH-recognition sites were located upstream of and within gluP, respectively. Transcriptional glucokinase operon--lacZ fusions and Northern blotting were used to analyze the expression of gluP. GluP was predicted to be an integral membrane protein. Moreover, the prediction of GluP structure revealed interesting signatures: a rhomboid domain and two tetracopeptide repeat (TPR) motifs. Microscopic analysis showed that GluP minus cells were unable to divide completely, resulting in a filamentous phenotype. The cells were grown in either rich or minimal medium. We found GluP may be involved in glucose transport. [14C]-glucose uptake by the GluP minus strain was slightly less than in the wild type. On the other hand, trehalose-derived glucose in the growth medium of the GluP minus strain was detected in very low amounts. Experimental controls comprised of single or multiple genes mutations within the glucose transporting phosphotransferase system.


CONCLUSIONS
gluP seems to be regulated only by a putative sigmaA-dependent promoter. The glucose uptake and export assays suggest that GluP is important for glucose export and may act as an exporter. This also supports the role of the glucokinase operon in glucose utilization.
Mesak
Lili R
LR
Department of Microbiology, Institute for Microbiology, Biochemistry and Genetics University of Erlangen-Nuremberg, Staudstrasse 5, 91058 Erlangen, Germany. lrmesak@yahoo.com
Mesak
Felix M
FM
Dahl
Michael K
MK
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000166:cytology / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D001692:Biological Transport; D002455:Cell Division; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D005941:Glucokinase / Q000235:genetics; D005947:Glucose / Q000378:metabolism*; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D009876:Operon; D000074435:Peroxisome-Targeting Signal 1 Receptor; D011401:Promoter Regions, Genetic; D017434:Protein Structure, Tertiary; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry; D020449:Repetitive Sequences, Amino Acid; D013171:Spores, Bacterial / Q000502:physiology
D001426:Bacterial Proteins; D009004:Monosaccharide Transport Proteins; D000074435:Peroxisome-Targeting Signal 1 Receptor; D018160:Receptors, Cytoplasmic and Nuclear; D005941:Glucokinase; D005947:Glucose