Affiliation:
1. Department of Molecular Biology, School of Health Sciences, Kyorin University, 476 Miyashita, Hachioji, Tokyo, 192-8508, Japan
Abstract
ABSTRACT
In members of one of the subfamilies of the bacterial ATP binding cassette (ABC) transporters, the two nucleotide binding domains are fused as a single peptide and the proteins have no membrane-spanning domain partners. Most of the ABC efflux transporters of this subfamily have been characterized in actinomycetes, producing macrolide, lincosamide, and streptogramin antibiotics. Among 40 ABC efflux transporters of
Bacillus subtilis
, five proteins belong to this subfamily. None of these proteins has been functionally characterized. We examined macrolide, lincosamide, and streptogramin antibiotic resistance in insertional disruptants of the genes that encode these proteins. It was found that only a disruptant of
vmlR
(formerly named
expZ
) showed hypersensitivity to virginiamycin M and lincomycin. Expression of the
vmlR
gene was induced by the addition of these antibiotics in growth medium. Primer extension analysis revealed that transcription of the
vmlR
gene initiates at an adenosine residue located 225 bp upstream of the initiation codon. From the analysis of the
vmlR
and
lacZ
fusion genes, a 52-bp deletion from +159 to +211 resulted in constitutive expression of the
vmlR
gene. In this region, a typical ρ-independent transcriptional terminator was found. It was suggested that the majority of transcription ends at this termination signal in the absence of antibiotics, whereas under induced conditions, RNA polymerase reads through the terminator, and transcription continues to the downstream
vmlR
coding region, resulting in an increase in
vmlR
expression. No stabilization of
vmlR
mRNA occurred under the induced conditions.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
37 articles.
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