title: Pal lipoprotein of Escherichia coli plays a major role in outer membrane integrity.
abstract: The Tol-Pal system of gram-negative bacteria is composed of five proteins. TolA, TolQ, and TolR are inner membrane proteins, TolB is a periplasmic protein, and Pal, the peptidoglycan-associated lipoprotein, is anchored to the outer membrane. In this study, the roles of Pal and major lipoprotein Lpp were compared in Escherichia coli. lpp and tol-pal mutations have previously been found to perturb the outer membrane permeability barrier and to cause the release of periplasmic proteins and the formation of outer membrane vesicles. In this study, we showed that the overproduction of Pal is able to restore the outer membrane integrity of an lpp strain but that overproduced Lpp has no effect in a pal strain. Together with the previously reported observation that overproduced TolA complements an lpp but not a pal strain, these results indicate that the cell envelope integrity is efficiently stabilized by an epistatic Tol-Pal system linking inner and outer membranes. The density of Pal was measured and found to be lower than that of Lpp. However, Pal was present in larger amounts compared to TolA and TolR proteins. The oligomeric state of Pal was determined and a new interaction between Pal and Lpp was demonstrated.
authors.affiliation: Laboratoire d'Ingéniérie des Systèmes Macromoléculaires, Institut de Biologie Structurale et de Microbiologie, CNRS, UPR 9027, 31 Chemin Joseph Aiguier, 13402 Marseille Cedex 20, France.
authors.forename: Eric
authors.initials: E
authors.lastname: Cascales
authors.forename: Alain
authors.initials: A
authors.lastname: Bernadac
authors.forename: Marthe
authors.initials: M
authors.lastname: Gavioli
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Lazzaroni
authors.forename: Roland
authors.initials: R
authors.lastname: Lloubes
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D002462:Cell Membrane / Q000502:physiology*; D002473:Cell Wall / Q000502:physiology*; D019281:Dimerization; D004926:Escherichia coli / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000378:metabolism; D005656:Fungal Proteins / Q000378:metabolism; D018628:Gene Dosage; D008074:Lipoproteins / Q000502:physiology*; D010457:Peptidoglycan; D011485:Protein Binding; D011509:Proteoglycans; D011994:Recombinant Proteins
chemical_list: D001425:Bacterial Outer Membrane Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; C031163:ExcC protein, E coli; D005656:Fungal Proteins; D008074:Lipoproteins; C099932:Lpp protein, E coli; D010457:Peptidoglycan; D011509:Proteoglycans; D011994:Recombinant Proteins; C117550:TOL protein, Neurospora crassa; C069988:PplA protein, Legionella pneumophila; C078167:OMPA outer membrane proteins