Affiliation:
1. Department of Bioscience, Fukui Prefectural University, 4-1-1 Matsuoka-Kenjojima, Eiheiji-cho, Fukui 910-1195
2. Department of Cell Membrane Biology, Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki-shi, Osaka 567-0047, Japan
Abstract
ABSTRACT
l
-Cysteine is an important amino acid in terms of its industrial applications. We previously found a marked production of
l
-cysteine from glucose in recombinant
Escherichia coli
cells expressing an altered
cysE
gene encoding feedback inhibition-insensitive serine acetyltransferase. Also, a lower level of cysteine desulfhydrase (CD) activity, which is involved in
l
-cysteine degradation, increased
l
-cysteine productivity in
E. coli
. The use of an
l
-cysteine efflux system could be promising for breeding
l
-cysteine overproducers. In addition to YdeD and YfiK, which have been reported previously as
l
-cysteine exporter proteins in
E. coli
, we analyzed the effects of 33 putative drug transporter genes in
E. coli
on
l
-cysteine export and overproduction. Overexpression of the
acrD
,
acrEF
,
bcr
,
cusA
,
emrAB
,
emrKY
,
ybjYZ
, and
yojIH
genes reversed the growth inhibition of
tnaA
(the major CD gene)-disrupted
E. coli
cells by
l
-cysteine. We also found that overexpression of these eight genes reduces intracellular
l
-cysteine levels after cultivation in the presence of
l
-cysteine. Amino acid transport assays showed that Bcr overexpression conferring bicyclomycin and tetracycline resistance specifically promotes
l
-cysteine export driven by energy derived from the proton gradient. When a
tnaA
-disrupted
E. coli
strain expressing the altered
cysE
gene was transformed with a plasmid carrying the
bcr
gene, the transformant exhibited more
l
-cysteine production than cells carrying the vector only. A reporter gene assay suggested that the
bcr
gene is constitutively expressed at a substantial level. These results indicate that the multidrug transporter Bcr in the major facilitator family is involved in
l
-cysteine export and overproduction in genetically engineered
E. coli
cells.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
62 articles.
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