In vivo and in vitro studies of the inhibition of the channel activity of colicins by gadolinium.
The primary effects of the ionophoric colicins A, E1 and B on Escherichia coli cells include triggering an efflux of cytoplasmic potassium, and a decrease of internal ATP as consequences of the opening of ionic channels in the cytoplasmic membrane. We report that micromolar concentrations of gadolinium and other members of the lanthanide family inhibited the efflux of potassium and the ATP decrease and that the cells recovered both ATP and potassium within a few minutes. Gadolinium, in the same concentration range also efficiently inhibited the channel activity of colicins A, E1, B and of the isolated channel-forming domain of colicin A in planar lipid bilayers. Colicin N was much less sensitive to the trivalent ion in planar lipid bilayers, consistent with the lack of effect of gadolinium on this colicin in vivo. Our data suggest that lanthanide ions act by direct binding to the colicin molecule and that this binding affects both its single-channel conductance and gating behaviour.
Bonhivers
M
M
Laboratoire des Biomembranes, URA CNRS 1116 Université Paris Sud, Orsay, France.
Guihard
G
G
Pattus
F
F
Letellier
L
L
D003087:Colicins / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism; D005682:Gadolinium / Q000494:pharmacology*; D007473:Ion Channels / Q000187:drug effects*; D017136:Ion Transport; D008051:Lipid Bilayers / Q000378:metabolism
D003087:Colicins; D007473:Ion Channels; D008051:Lipid Bilayers; D005682:Gadolinium