Excretion and uptake of cadaverine by CadB and its physiological functions in Escherichia coli.
The functions of the putative cadaverine transport protein CadB were studied in Escherichia coli. CadB had both cadaverine uptake activity, dependent on proton motive force, and cadaverine excretion activity, acting as a cadaverine-lysine antiporter. The Km values for uptake and excretion of cadaverine were 20.8 and 303 microM respectively. Both cadaverine uptake and cadaverine-lysine antiporter activities of CadB were functional in cells. Cell growth of a polyamine-requiring mutant was stimulated slightly at neutral pH by the cadaverine uptake activity and greatly at acidic pH by the cadaverine-lysine antiporter activity. At acidic pH, the operon containing cadB and cadA, encoding lysine decarboxylase, was induced in the presence of lysine. This caused neutralization of the extracellular medium and made possible the production of CO(2) and cadaverine and aminopropylcadaverine instead of putrescine and spermidine. The induction of the cadBA operon also generated a proton motive force. When the cadBA operon was not induced, the expression of the speF-potE operon, encoding inducible ornithine decarboxylase and a putrescine-ornithine antiporter, was increased. The results indicate that the cadBA operon plays important roles in cellular regulation at acidic pH.
Graduate School of Pharmaceutical Sciences, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan.
Waraporn
W
Soksawatmaekhin
Aiko
A
Kuraishi
Kaori
K
Sakata
Keiko
K
Kashiwagi
Kazuei
K
Igarashi
D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D026905:Amino Acid Transport Systems / Q000235:genetics / Q000378:metabolism*; D017920:Antiporters / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport / Q000502:physiology; D002103:Cadaverine / Q000378:metabolism*; D002455:Cell Division; D002462:Cell Membrane / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007476:Ionophores / Q000378:metabolism; D008969:Molecular Sequence Data; D009876:Operon; D011073:Polyamines / Q000378:metabolism; D016415:Sequence Alignment
D026905:Amino Acid Transport Systems; D017920:Antiporters; D001426:Bacterial Proteins; C088101:CadB protein, Bacteria; C490242:CadB protein, E Coli; D029968:Escherichia coli Proteins; D007476:Ionophores; D011073:Polyamines; C071519:PotE protein, E coli; D000255:Adenosine Triphosphate; D002103:Cadaverine