Functional properties of Kch, a prokaryotic homologue of eukaryotic potassium channels.
To test the hypothesis that the Kch gene of Escherichia coli encodes a potassium channel, we have transformed E. coli with an expression vector containing the Kch sequence and observed the effect of over-expression of Kch on E. coli. We found that: (i) over-expression of Kch is toxic to E. coli, but the toxicity could be prevented by supplementing the growth medium with K(+), Rb(+), and NH(4)(+), but not Na(+), consistent with the properties of a potassium selective pore; (ii) Cs(+), a blocker of potassium channels, rescues the growth of Kch over-expressing cells; and (iii) when the putative pore-forming region of Kch, containing the signature sequence, was replaced with the corresponding region of the eukaryotic Shaker potassium channel, and the resultant construct expressed in E. coli, the cells became critically dependent on K(+) supply for survival. These data are consistent with the proposed function of Kch, i.e., K(+) conduction.
Munsey
Tim S
TS
School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom.
Mohindra
Atul
A
Yusaf
Shahnaz P
SP
Grainge
Alison
A
Wang
Myeong-H
MH
Wray
Dennis
D
Sivaprasadarao
Asipu
A
D000818:Animals; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins; D009865:Oocytes / Q000378:metabolism; D010957:Plasmids / Q000235:genetics; D011188:Potassium / Q000494:pharmacology; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D013045:Species Specificity; D014162:Transfection; D014981:Xenopus
D029968:Escherichia coli Proteins; D026902:Potassium Channel Blockers; D015221:Potassium Channels; C101871:kch protein, E coli; D011188:Potassium