RRC ID 35549
著者 Holdsworth SR, Law CJ.
タイトル Multidrug resistance protein MdtM adds to the repertoire of antiporters involved in alkaline pH homeostasis in Escherichia coli.
ジャーナル BMC Microbiol
Abstract BACKGROUND:In neutralophilic bacteria, monovalent metal cation/H+ antiporters play a key role in pH homeostasis. In Escherichia coli, only four antiporters (NhaA, NhaB, MdfA and ChaA) are identified to function in maintenance of a stable cytoplasmic pH under conditions of alkaline stress. We hypothesised that the multidrug resistance protein MdtM, a recently characterised homologue of MdfA and a member of the major facilitator superfamily, also functions in alkaline pH homeostasis.
RESULTS:Assays that compared the growth of an E. coli ΔmdtM deletion mutant transformed with a plasmid encoding wild-type MdtM or the dysfunctional MdtM D22A mutant at different external alkaline pH values (ranging from pH 8.5 to 10) revealed a potential contribution by MdtM to alkaline pH tolerance, but only when millimolar concentrations of sodium or potassium was present in the growth medium. Fluorescence-based activity assays using inverted vesicles generated from transformants of antiporter-deficient (ΔnhaA, ΔnhaB, ΔchaA) E. coli TO114 cells defined MdtM as a low-affinity antiporter that catalysed electrogenic exchange of Na+, K+, Rb+ or Li+ for H+. The K+/H+ antiport reaction had a pH optimum at 9.0, whereas the Na+/H+ exchange activity was optimum at pH 9.25. Measurement of internal cellular pH confirmed MdtM as contributing to maintenance of a stable cytoplasmic pH, acid relative to the external pH, under conditions of alkaline stress.
CONCLUSIONS:Taken together, the results support a role for MdtM in alkaline pH tolerance. MdtM can therefore be added to the currently limited list of antiporters known to function in pH homeostasis in the model organism E. coli.
巻・号 13
ページ 113
公開日 2013-5-23
DOI 10.1186/1471-2180-13-113
PII 1471-2180-13-113
PMID 23701827
PMC PMC3668916
MeSH Alkalies / metabolism* Antiporters / genetics Antiporters / metabolism* Cations / metabolism Escherichia coli / genetics Escherichia coli / growth & development Escherichia coli / metabolism Escherichia coli / physiology* Escherichia coli Proteins / genetics Escherichia coli Proteins / metabolism* Gene Deletion Genetic Complementation Test Homeostasis* Hydrogen-Ion Concentration Metals / metabolism
IF 2.989
引用数 24
WOS 分野 MICROBIOLOGY
リソース情報
原核生物(大腸菌) ME9062(BW25113)(Keio collection)