Open AccessIdentification of a Spermidine Excretion Protein Complex (MdtJI) in Escherichia coli
Author(s) -
Kyohei Higashi,
Hiroyuki Ishigure,
Risa Demizu,
Takeshi Uemura,
Kunihiko Nishino,
Akihito Yamaguchi,
Keiko Kashiwagi,
Kazuei Igarashi
Publication year - 2008
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.01505-07
Subject(s) - spermidine , biology , excretion , biochemistry , escherichia coli , putrescine , polyamine , enzyme , microbiology and biotechnology , gene
A spermidine excretion protein inEscherichia coli was looked for among 33 putative drug exporters thus far identified. Cell toxicity and inhibition of growth due to overaccumulation of spermidine were examined in anE. coli strain deficient in spermidine acetyltransferase, an enzyme that metabolizes spermidine. Toxicity and inhibition of cell growth by spermidine were recovered in cells transformed with pUCmdtJI or pMWmdtJI , encoding MdtJ and MdtI, which belong to the small multidrug resistance family of drug exporters. BothmdtJ andmdtI are necessary for recovery from the toxicity of overaccumulated spermidine. It was also found that the level ofmdtJI mRNA was increased by spermidine. The spermidine content in cells cultured in the presence of 2 mM spermidine was decreased, and excretion of spermidine from cells was enhanced by MdtJI, indicating that the MdtJI complex can catalyze excretion of spermidine from cells. It was found that Tyr4 , Trp5 , Glu15 , Tyr45 , Tyr61 , and Glu82 in MdtJ and Glu5 , Glu19 , Asp60 , Trp68 , and Trp81 in MdtI are involved in the excretion activity of MdtJI.