PMID:7608059

Citation	Ahmed, M, Lyass, L, Markham, PN, Taylor, SS, Vázquez-Laslop, N and Neyfakh, AA (1995) Two highly similar multidrug transporters of Bacillus subtilis whose expression is differentially regulated. J. Bacteriol. 177:3904-10
Abstract	The Bacillus subtilis genome encodes two multidrug efflux transporters sharing 51% sequence identity: Bmr, described previously, and Blt, described here. Overexpression of either transporter in B. subtilis leads to a similar increase in resistance to ethidium bromide, rhodamine and acridine dyes, tetraphenylphosphonium, doxorubicin, and fluoroquinolone antibiotics. However, Blt differs widely from Bmr in its expression pattern. Under standard cultivation conditions, B. subtilis expresses Bmr but Blt expression is undetectable. We have previously shown that Bmr expression is regulated by BmrR, a member of the family of MerR-like transcriptional activators. Here we show that blt transcription is regulated by another member of the same family, BltR. The DNA-binding domains of BmrR and BltR are related, but their putative inducer-binding domains are dissimilar, suggesting that Bmr and Blt are expressed in response to different inducers. Indeed, rhodamine, a substrate of Bmr and Blt and a known inducer of Bmr expression, does not induce Blt expression. Blt expression has been observed only in B. subtilis, carrying mutation acfA, which, as we show here, alters the sequence of the blt gene promoter. Unlike bmr, which is transcribed as a monocistronic mRNA, blt is cotranscribed with a downstream gene encoding a putative acetyltransferase. Overall, the differences in transcriptional control and operon organization between bmr and blt suggest that the transporters encoded by these genes have independent functions involving the transport of distinct physiological compounds.
Links	PubMed PMC177116
Keywords	Acetyltransferases/genetics; Amino Acid Sequence; Bacillus subtilis/drug effects; Bacillus subtilis/genetics; Bacterial Proteins/genetics; Base Sequence; Biological Transport; Blotting, Northern; Carrier Proteins/genetics; Cloning, Molecular; Drug Resistance, Microbial/genetics; Drug Resistance, Multiple/genetics; Gene Expression Regulation, Bacterial; Genes, Regulator/genetics; Membrane Transport Proteins; Molecular Sequence Data; Polymerase Chain Reaction; Promoter Regions, Genetic/genetics; Sequence Analysis, DNA; Sequence Homology, Amino Acid; Trans-Activators/genetics; Transcription, Genetic
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
BACSU:BMR1		GO:0046677: response to antibiotic	ECO:0000315:		P		Figure 4: Overexpression of the gene bmr exhibited degrees of resistance to the antibiotics present in the experiment.	complete
BACSU:BMR2		GO:0046677: response to antibiotic	ECO:0000315:		P		Figure 4: Overexpression of the gene blt exhibited degrees of resistance to the antibiotics present in the experiment.	complete

References

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