Open AccessRole of acidic lipids in the translocation and channel activity of colicins A and N in Escherichia coli cells
Author(s) -
GOOT F. Gisou,
DIDAT Nathalie,
PATTUS Franc,
DOWHAN William,
LETELLIER Lucienne
Publication year - 1993
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1993.tb17751.x
Subject(s) - colicin , cell envelope , escherichia coli , efflux , biophysics , periplasmic space , bacterial outer membrane , cytoplasm , inner membrane , biochemistry , chromosomal translocation , biology , chemistry , cell membrane , membrane , microbiology and biotechnology , gene
Colicins A and N are pore‐forming bacterial toxins that kill Escherichia coli cells. Their mode of action involves three steps; binding to specific receptors located in the outer membrane, translocation through this membrane and the periplasm, and channel formation in the inner membrane. In‐vitro studies have shown that negatively charged phospholipids are an absolute requirement for the channel formation of colicin A. Using HDL11 strain, in which the phosphatidylglycerol (PtdGro) content was altered by varying the synthesis of the PtdGro‐phosphate synthase, the effect of envelope PtdGro content on the activity of colicin A was studied in vivo . The formation by colicin A of a voltage‐gated channel in the cytoplasmic membrane results in an efflux of cytoplasmic potassium. This efflux is preceded by a lag time which is related to the time needed by the toxin to cross the cell envelope. This lag time is higher when the cells have a reduced PtdGro level, suggesting that the receptor/translocation machinery of colicin A (OmpF, BtuB and Tol QRAB proteins) is altered in the absence of PtdGro. The rate of potassium efflux is also greatly reduced when the PtdGro content is decreased, suggesting that a certain level of PtdGro is indeed required for proper insertion of the colicin‐A channel. In contrast, the activity of colicin N does not show any PtdGro dependence. The difference between the behavior of colicin A and that of colicin N is discussed.