Peptidoglycan-associated lipoprotein-TolB interaction. A possible key to explaining the formation of contact sites between the inner and outer membranes of Escherichia coli.
TolA, -B, -Q, and -R proteins are involved in maintaining the cell envelope integrity of Escherichia coli; they have been parasitized by the group A colicins and the single strand DNA of some filamentous bacteriophages to permit them to enter the cells. TolA and TolR are anchored to the inner membrane by a single transmembrane domain, TolQ is an integral membrane protein with three transmembrane segments, and TolB has recently been found to be periplasmic although it is partially membrane-associated. The latter result suggests that TolB might interact with membrane proteins. Other lines of evidence favor the existence of a Tol complex. To further characterize this complex, we investigated which proteins interact with TolB. For this purpose, two different methods were used. First, we took advantage of the existence of a tagged TolB (TolBep) to perform immunoprecipitation under native conditions in order to preserve the putative associations of TolBep with other proteins. Secondly, in vivo cross-linking experiments with formaldehyde were performed. These two approaches led to the same result and demonstrated for the first time that a component of the Tol system, TolB, interacts with a protein located in the outer membrane, the peptidoglycan-associated lipoprotein.
Bouveret
E
E
Laboratoire d'Ingénierie et de Dynamique des Systèmes Membranaires, CNRS, Marseille, France.
Derouiche
R
R
Rigal
A
A
Lloubès
R
R
Lazdunski
C
C
Bénédetti
H
H
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins / Q000302:isolation & purification / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D003432:Cross-Linking Reagents; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins; D005557:Formaldehyde; D005838:Genotype; D015151:Immunoblotting; D008074:Lipoproteins / Q000302:isolation & purification / Q000378:metabolism*; D008561:Membrane Fusion; D008565:Membrane Proteins / Q000378:metabolism*; D008715:Methionine / Q000378:metabolism; D008970:Molecular Weight; D010457:Peptidoglycan / Q000302:isolation & purification / Q000378:metabolism*; D033903:Periplasmic Proteins; D010641:Phenotype; D010957:Plasmids; D011509:Proteoglycans; D013462:Sulfur Radioisotopes
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D003432:Cross-Linking Reagents; D029968:Escherichia coli Proteins; C031163:ExcC protein, E coli; D008074:Lipoproteins; D008565:Membrane Proteins; D010457:Peptidoglycan; D033903:Periplasmic Proteins; D011509:Proteoglycans; D013462:Sulfur Radioisotopes; C062094:tolB protein, E coli; C069988:PplA protein, Legionella pneumophila; D005557:Formaldehyde; D008715:Methionine