期刊
JOURNAL OF BACTERIOLOGY
卷 187, 期 6, 页码 1923-1929出版社
AMER SOC MICROBIOLOGY
DOI: 10.1128/JB.187.6.1923-1929.2005
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资金
- NIAID NIH HHS [R37 AI009644, AI-09644, R01 AI009644] Funding Source: Medline
To understand better the mechanisms of resistance-nodulation-division (RND)-type multidrug efflux pumps, we examined the Escherichia coli AcrD pump, whose typical substrates, aminoglycosides, are not expected to diffuse spontaneously across the lipid bilayer. The hexahistidine-tagged AcrD protein was purified and reconstituted into unilamellar proteoliposomes. Its activity was measured by the proton flux accompanying substrate transport. When the interior of the proteolliposomes was acidified, the addition of aminoglycosides to the external medium stimulated proton efflux and the intravesicular accumulation of radiolabeled gentamicin, suggesting that aminoglycosides can be captured and transported from the external medium in this system (corresponding to cytosol). This activity required the presence of AcrA within the proteolliposomes. Interestingly, the increase in proton efflux illso occurred when aminoglycosides were present only in the intravesicular space. This result suggested that AcrD can also capture aminoglycosides from the periplasm to extrude them into the medium in intact cells, acting as a periplasmic vacuum cleaner.
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