N. Didat

Publications (3)3.58 Total impact

• Chapter: Puncturing Cell Membranes: Comparison of Colicin A and Aerolysin

  N. Didat, J. M. Gonzàlez-mañas, F. G. Van Der Goot, D. Jeanteur, J. H. Lakey, F. Pattus, D. Massotte, S. Scianimanico, H.-U. Wilmsen
  [show abstract] [hide abstract]
  ABSTRACT: Colicin A from Citrobacter freundii and aerolysin from Aeromonas hydrophila are representatives of two classes of pore-forming toxins. Colicin A, an alpha-helical protein, contains a hydrophobic hairpin Colicin A from Citrobacter freundii and aerolysin from Aeromonas hydrophila are representatives of two classes of pore-forming toxins. Colicin A, an alpha-helical protein, contains a hydrophobic hairpin which is buried inside the structure in solution. It is an “inside out” membrane protein. Aerolysin is formed almost exclusively which is buried inside the structure in solution. It is an “inside out” membrane protein. Aerolysin is formed almost exclusively by β-sheets and possesses a very hydrophilic amino acid sequence. It is secreted as an inactive precursor which is activated by β-sheets and possesses a very hydrophilic amino acid sequence. It is secreted as an inactive precursor which is activated by proteolytic removal of about 43-41 residues from the C-terminus. The mechanism of membrane insertion and the structure by proteolytic removal of about 43-41 residues from the C-terminus. The mechanism of membrane insertion and the structure of the membrane bound form of these toxins are discussed. of the membrane bound form of these toxins are discussed.
  03/2011: pages 393-401;
• Article: Role of acidic lipids in the translocation and channel activity of colicins A and N in Escherichia coli cells.

  F G van der Goot, N Didat, F Pattus, W Dowhan, L Letellier
  [show abstract] [hide abstract]
  ABSTRACT: 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.
  European Journal of Biochemistry 05/1993; 213(1):217-21. · 3.58 Impact Factor
• Article: Puncturing cell membranes : comparison of colicin A and Aerolysin

  A. Pullman, N. Didat, J.-M. Gonzales-Manas, F. G. van der Goot, D Jeanteur, F. Lakey, F Pattus, H. U. Wilsen