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J. Bacteriol., Mar 1995, 1536-1543, Vol 177, No. 6
K Nagao, Y Taguchi, M Arioka, H Kadokura, A Takatsuki, K Yoda and M Yamasaki
We have isolated a Schizosaccharomyces pombe gene, bfr1+, which on a
multicopy plasmid vector, pDB248', confers resistance to brefeldin A (BFA),
an inhibitor of intracellular protein transport. This gene encodes a novel
protein of 1,531 amino acids with an intramolecular duplicated structure,
each half containing a single ATP-binding consensus sequence and a set of
six transmembrane sequences. This structural characteristic of bfr1+
protein resembles that of mammalian P-glycoprotein, which, by exporting a
variety of anticancer drugs, has been shown to be responsible for multidrug
resistance in tumor cells. Consistent with this is that S. pombe cells
harboring bfr1+ on pDB248' are resistant to actinomycin D, cerulenin, and
cytochalasin B, as well as to BFA. The relative positions of the
ATP-binding sequences and the clusters of transmembrane sequences within
the bfr1+ protein are, however, transposed in comparison with those in
P-glycoprotein; the bfr1+ protein has N-terminal ATP-binding sequence
followed by transmembrane segments in each half of the molecule. The bfr1+
protein exhibited significant homology in primary and secondary structures
with two recently identified multidrug resistance gene products of
Saccharomyces cerevisiae, Snq2 and Sts1/Pdr5/Ydr1. The bfr1+ gene is not
essential for cell growth or mating, but a delta bfr1 mutant exhibited
hypersensitivity to BFA. We propose that the bfr1+ protein is another
member of the ATP-binding cassette superfamily and serves as an efflux pump
of various antibiotics.
Copyright © 1995, American Society for Microbiology
bfr1+, a novel gene of Schizosaccharomyces pombe which confers brefeldin A resistance, is structurally related to the ATP-binding cassette superfamily
Department of Biotechnology, University of Tokyo, Japan.
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