Histidine 440 controls the opening of colicin E1 channels in a lipid-dependent manner.
The in vitro activity of many pore-forming toxins, in particular, the rate of increase in the membrane conductance induced by the channel-forming domain (P178) of colicin E1 is maximum at an acidic pH. However, after P178 binding at acidic conditions, a subsequent pH shift from 4 to 6 on both sides of the planar bilayer lipid membrane caused a large increase in the trans-membrane current which was solely due to an increase in the number of open channels. This effect required the presence of anionic lipid. Replacing the His440 residue of P178 by alanine eliminated the pH-shift effect thereby showing that it is associated with deprotonation of this histidine residue. It was concluded that alkalinization-induced weakening of the electrostatic interactions between colicin and the membrane surface facilitates conformational changes required for the transition of membrane-bound colicin molecules to an active channel state.
Sobko
Alexander A
AA
A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119991, Russia. sobko@genebee.msu.ru
Rokitskaya
Tatyana I
TI
Kotova
Elena A
EA
D000595:Amino Acid Sequence; D003087:Colicins / Q000378:metabolism*; D006639:Histidine / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D015640:Ion Channel Gating / Q000187:drug effects*; D008051:Lipid Bilayers / Q000378:metabolism*; D008969:Molecular Sequence Data
D003087:Colicins; D008051:Lipid Bilayers; D006639:Histidine